diff --git a/core/src/main/java/uk/gov/gchq/koryphe/impl/function/CsvLinesToMaps.java b/core/src/main/java/uk/gov/gchq/koryphe/impl/function/CsvLinesToMaps.java
index 4fdeab532..4d46a6b18 100644
--- a/core/src/main/java/uk/gov/gchq/koryphe/impl/function/CsvLinesToMaps.java
+++ b/core/src/main/java/uk/gov/gchq/koryphe/impl/function/CsvLinesToMaps.java
@@ -27,7 +27,6 @@
 import uk.gov.gchq.koryphe.Since;
 import uk.gov.gchq.koryphe.Summary;
 import uk.gov.gchq.koryphe.function.KorypheFunction;
-import uk.gov.gchq.koryphe.iterable.CloseableIterable;
 import uk.gov.gchq.koryphe.util.IterableUtil;
 
 import java.io.IOException;
@@ -45,10 +44,10 @@
 
 @Since("1.8.0")
 @Summary("Parses CSV lines into Maps")
-@JsonPropertyOrder(value = {"header", "firstRow", "delimiter", "quoted", "quoteChar"},
-        alphabetic = true)
+@JsonPropertyOrder(value = { "header", "firstRow", "delimiter", "quoted", "quoteChar" }, alphabetic = true)
 @JsonInclude(JsonInclude.Include.NON_DEFAULT)
-public class CsvLinesToMaps extends KorypheFunction<Iterable<String>, Iterable<Map<String, Object>>> implements Serializable {
+public class CsvLinesToMaps extends KorypheFunction<Iterable<String>, Iterable<Map<String, Object>>>
+        implements Serializable {
     private static final long serialVersionUID = -4225921410795200955L;
     private List<String> header = new ArrayList<>();
     private int firstRow = 0;
@@ -62,7 +61,7 @@ public Iterable<Map<String, Object>> apply(final Iterable<String> csvStrings) {
             return null;
         }
 
-        final CloseableIterable<String> csvRecords = IterableUtil.limit(csvStrings, firstRow, null, false);
+        final Iterable<String> csvRecords = IterableUtil.limit(csvStrings, firstRow, null, false);
         return IterableUtil.map(csvRecords, (item) -> createMap((String) item));
     }
 
@@ -81,8 +80,8 @@ private Map<String, Object> extractMap(final CSVRecord csvRecord) {
 
     private CSVRecord parseCsv(final String csv) {
         final CSVRecord csvRecord;
-        try {
-            csvRecord = new CSVParser(new StringReader(csv), getCsvFormat()).iterator().next();
+        try (final CSVParser csvParser = new CSVParser(new StringReader(csv), getCsvFormat())) {
+            csvRecord = csvParser.iterator().next();
         } catch (final IOException e) {
             throw new RuntimeException(e);
         }
@@ -91,8 +90,7 @@ private CSVRecord parseCsv(final String csv) {
             throw new IllegalArgumentException(
                     "CSV has " + csvRecord.size()
                             + " columns, but there are " + header.size()
-                            + " provided column names"
-            );
+                            + " provided column names");
         }
         return csvRecord;
     }
@@ -192,7 +190,7 @@ public boolean equals(final Object o) {
             return false; // Does class checking
         }
 
-        CsvLinesToMaps that = (CsvLinesToMaps) o;
+        final CsvLinesToMaps that = (CsvLinesToMaps) o;
         return new EqualsBuilder()
                 .append(header, that.header)
                 .append(quoted, that.quoted)
diff --git a/core/src/main/java/uk/gov/gchq/koryphe/impl/function/CsvToMaps.java b/core/src/main/java/uk/gov/gchq/koryphe/impl/function/CsvToMaps.java
index 1af340104..047f0aa93 100644
--- a/core/src/main/java/uk/gov/gchq/koryphe/impl/function/CsvToMaps.java
+++ b/core/src/main/java/uk/gov/gchq/koryphe/impl/function/CsvToMaps.java
@@ -27,7 +27,7 @@
 import uk.gov.gchq.koryphe.Since;
 import uk.gov.gchq.koryphe.Summary;
 import uk.gov.gchq.koryphe.function.KorypheFunction;
-import uk.gov.gchq.koryphe.iterable.CloseableIterable;
+import uk.gov.gchq.koryphe.util.CloseableUtil;
 import uk.gov.gchq.koryphe.util.IterableUtil;
 
 import java.io.IOException;
@@ -45,8 +45,7 @@
 
 @Since("1.8.0")
 @Summary("Parses a CSV into Maps")
-@JsonPropertyOrder(value = {"header", "firstRow", "delimiter", "quoted", "quoteChar"},
-        alphabetic = true)
+@JsonPropertyOrder(value = { "header", "firstRow", "delimiter", "quoted", "quoteChar" }, alphabetic = true)
 @JsonInclude(JsonInclude.Include.NON_DEFAULT)
 public class CsvToMaps extends KorypheFunction<String, Iterable<Map<String, Object>>> implements Serializable {
     private static final long serialVersionUID = 891938487168606844L;
@@ -62,12 +61,14 @@ public Iterable<Map<String, Object>> apply(final String csv) {
             return null;
         }
 
-        try {
-            final CSVParser csvParser = new CSVParser(new StringReader(csv), getCsvFormat());
-            final CloseableIterable<CSVRecord> csvRecords = IterableUtil.limit(csvParser.getRecords(), firstRow, null, false);
-            return IterableUtil.map(csvRecords, item -> extractMap((CSVRecord) item));
+        Iterable<CSVRecord> csvRecords = null;
+        try (final CSVParser csvParser = new CSVParser(new StringReader(csv), getCsvFormat())) {
+            csvRecords = IterableUtil.limit(csvParser.getRecords(), firstRow, null, false);
+            return IterableUtil.map(csvRecords, (item) -> extractMap((CSVRecord) item));
         } catch (final IOException e) {
             throw new RuntimeException("Unable to parse csv", e);
+        } finally {
+            CloseableUtil.close(csvRecords);
         }
     }
 
@@ -163,6 +164,7 @@ public CsvToMaps quoteChar(final char quoteChar) {
         this.quoteChar = quoteChar;
         return this;
     }
+
     @Override
     public boolean equals(final Object o) {
         if (this == o) {
@@ -173,7 +175,7 @@ public boolean equals(final Object o) {
             return false; // Does class checking
         }
 
-        CsvToMaps that = (CsvToMaps) o;
+        final CsvToMaps that = (CsvToMaps) o;
         return new EqualsBuilder()
                 .append(header, that.header)
                 .append(quoted, that.quoted)
@@ -194,5 +196,4 @@ public int hashCode() {
                 .append(delimiter)
                 .toHashCode();
     }
-
 }
diff --git a/core/src/main/java/uk/gov/gchq/koryphe/impl/function/ToDouble.java b/core/src/main/java/uk/gov/gchq/koryphe/impl/function/ToDouble.java
new file mode 100644
index 000000000..0ab1821b7
--- /dev/null
+++ b/core/src/main/java/uk/gov/gchq/koryphe/impl/function/ToDouble.java
@@ -0,0 +1,49 @@
+/*
+ * Copyright 2022 Crown Copyright
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package uk.gov.gchq.koryphe.impl.function;
+
+import uk.gov.gchq.koryphe.Since;
+import uk.gov.gchq.koryphe.Summary;
+import uk.gov.gchq.koryphe.function.KorypheFunction;
+
+/**
+ * A <code>ToDouble</code> is a {@link java.util.function.Function} that takes
+ * an Object and casts it to a Double.
+ * <p>
+ * The resulting object is what is returned from the method.
+ */
+@Since("2.0.0")
+@Summary("Casts input Object to a Double")
+public class ToDouble extends KorypheFunction<Object, Double> {
+
+    @Override
+    public Double apply(final Object value) {
+        if (null == value) {
+            return null;
+        }
+
+        if (value instanceof Number) {
+            return ((Number) value).doubleValue();
+        }
+
+        if (value instanceof String) {
+            return Double.valueOf(((String) value));
+        }
+
+        throw new IllegalArgumentException("Could not convert value to Double: " + value);
+    }
+}
diff --git a/core/src/main/java/uk/gov/gchq/koryphe/iterable/CloseableIterable.java b/core/src/main/java/uk/gov/gchq/koryphe/iterable/CloseableIterable.java
deleted file mode 100644
index 4bac40ad9..000000000
--- a/core/src/main/java/uk/gov/gchq/koryphe/iterable/CloseableIterable.java
+++ /dev/null
@@ -1,35 +0,0 @@
-/*
- * Copyright 2016-2020 Crown Copyright
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package uk.gov.gchq.koryphe.iterable;
-
-import java.io.Closeable;
-
-/**
- * A {@code CloseableIterable} is an {@link Iterable} which must provide an implementation
- * of the {@link Closeable#close()} method.
- *
- * @param <T> the type of items in the iterable.
- * @deprecated Closable will be removed, it is used with scaling Big Data and does not belong in Koryphe.
- */
-@Deprecated
-public interface CloseableIterable<T> extends Iterable<T>, Closeable {
-    @Override
-    void close();
-
-    @Override
-    CloseableIterator<T> iterator();
-}
diff --git a/core/src/main/java/uk/gov/gchq/koryphe/iterable/CloseableIterator.java b/core/src/main/java/uk/gov/gchq/koryphe/iterable/CloseableIterator.java
deleted file mode 100644
index cd7346d0f..000000000
--- a/core/src/main/java/uk/gov/gchq/koryphe/iterable/CloseableIterator.java
+++ /dev/null
@@ -1,33 +0,0 @@
-/*
- * Copyright 2016-2020 Crown Copyright
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package uk.gov.gchq.koryphe.iterable;
-
-import java.io.Closeable;
-import java.util.Iterator;
-
-/**
- * A {@code CloseableIterator} is an {@link Iterator} which must provide an implementation
- * of the {@link Closeable#close()} method.
- *
- * @param <T> the type of items in the iterator.
- * @deprecated Closable will be removed, it is used with scaling Big Data and does not belong in Koryphe.
- */
-@Deprecated()
-public interface CloseableIterator<T> extends Iterator<T>, Closeable {
-    @Override
-    void close();
-}
diff --git a/core/src/main/java/uk/gov/gchq/koryphe/iterable/EmptyCloseableIterator.java b/core/src/main/java/uk/gov/gchq/koryphe/iterable/EmptyCloseableIterator.java
deleted file mode 100644
index 72b8d76c6..000000000
--- a/core/src/main/java/uk/gov/gchq/koryphe/iterable/EmptyCloseableIterator.java
+++ /dev/null
@@ -1,42 +0,0 @@
-/*
- * Copyright 2019-2020 Crown Copyright
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package uk.gov.gchq.koryphe.iterable;
-
-
-import java.util.NoSuchElementException;
-
-/**
- * @param <T> the type of items in the iterator.
- * @deprecated Closable will be removed, it is used with scaling Big Data and does not belong in Koryphe.
- */
-@Deprecated
-public class EmptyCloseableIterator<T> implements CloseableIterator<T> {
-    @Override
-    public void close() {
-        // nothing to close
-    }
-
-    @Override
-    public boolean hasNext() {
-        return false;
-    }
-
-    @Override
-    public T next() {
-        throw new NoSuchElementException();
-    }
-}
diff --git a/core/src/main/java/uk/gov/gchq/koryphe/iterable/StreamIterable.java b/core/src/main/java/uk/gov/gchq/koryphe/iterable/StreamIterable.java
deleted file mode 100644
index 7a5ae44cf..000000000
--- a/core/src/main/java/uk/gov/gchq/koryphe/iterable/StreamIterable.java
+++ /dev/null
@@ -1,52 +0,0 @@
-/*
- * Copyright 2019-2020 Crown Copyright
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package uk.gov.gchq.koryphe.iterable;
-
-import com.fasterxml.jackson.annotation.JsonIgnore;
-
-import uk.gov.gchq.koryphe.util.CloseableUtil;
-
-import java.util.function.Supplier;
-import java.util.stream.Stream;
-
-/**
- * @param <T> the type of items in the iterator.
- * @deprecated Closable will be removed, it is used with scaling Big Data and does not belong in Koryphe.
- */
-@Deprecated
-public class StreamIterable<T> implements CloseableIterable<T> {
-    private final Supplier<Stream<T>> streamSupplier;
-
-    public StreamIterable(final Supplier<Stream<T>> streamSupplier) {
-        this.streamSupplier = streamSupplier;
-    }
-
-    @Override
-    public void close() {
-        CloseableUtil.close(streamSupplier);
-    }
-
-    @Override
-    public CloseableIterator<T> iterator() {
-        return new StreamIterator<>(streamSupplier.get());
-    }
-
-    @JsonIgnore
-    public Stream<T> getStream() {
-        return streamSupplier.get();
-    }
-}
diff --git a/core/src/main/java/uk/gov/gchq/koryphe/iterable/StreamIterator.java b/core/src/main/java/uk/gov/gchq/koryphe/iterable/StreamIterator.java
deleted file mode 100644
index 2d35e0add..000000000
--- a/core/src/main/java/uk/gov/gchq/koryphe/iterable/StreamIterator.java
+++ /dev/null
@@ -1,71 +0,0 @@
-/*
- * Copyright 2019-2020 Crown Copyright
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package uk.gov.gchq.koryphe.iterable;
-
-import uk.gov.gchq.koryphe.util.CloseableUtil;
-
-import java.util.Iterator;
-import java.util.stream.Stream;
-
-/**
- * @param <T> the type of items in the iterator.
- * @deprecated Closable will be removed, it is used with scaling Big Data and does not belong in Koryphe.
- */
-@Deprecated
-public class StreamIterator<T> implements CloseableIterator<T> {
-    private final Stream<T> stream;
-    private final Iterator<T> iterator;
-
-    public StreamIterator() {
-        this(null);
-    }
-
-    public StreamIterator(final Stream<T> stream) {
-        if (null == stream) {
-            this.stream = Stream.empty();
-            this.iterator = new EmptyCloseableIterator<>();
-        } else {
-            this.stream = stream;
-            this.iterator = stream.iterator();
-        }
-    }
-
-    @Override
-    public void close() {
-        CloseableUtil.close(iterator);
-        CloseableUtil.close(stream);
-    }
-
-    @Override
-    public boolean hasNext() {
-        return iterator.hasNext();
-    }
-
-    @Override
-    public T next() {
-        return iterator.next();
-    }
-
-    @Override
-    public void remove() {
-        iterator.remove();
-    }
-
-    public Stream<T> getStream() {
-        return stream;
-    }
-}
diff --git a/core/src/main/java/uk/gov/gchq/koryphe/iterable/package-info.java b/core/src/main/java/uk/gov/gchq/koryphe/iterable/package-info.java
deleted file mode 100644
index 876eb0845..000000000
--- a/core/src/main/java/uk/gov/gchq/koryphe/iterable/package-info.java
+++ /dev/null
@@ -1,21 +0,0 @@
-/*
- * Copyright 2017-2020 Crown Copyright
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-/**
- * Gaffer-specific {@link java.lang.Iterable}s and {@link java.util.Iterator}s used when retrieving
- * and manipulating data from stores.
- */
-package uk.gov.gchq.koryphe.iterable;
diff --git a/core/src/main/java/uk/gov/gchq/koryphe/util/IterableUtil.java b/core/src/main/java/uk/gov/gchq/koryphe/util/IterableUtil.java
index 45d1f7b60..f6d4347ca 100644
--- a/core/src/main/java/uk/gov/gchq/koryphe/util/IterableUtil.java
+++ b/core/src/main/java/uk/gov/gchq/koryphe/util/IterableUtil.java
@@ -18,9 +18,8 @@
 import com.fasterxml.jackson.annotation.JsonIgnore;
 
 import uk.gov.gchq.koryphe.impl.predicate.And;
-import uk.gov.gchq.koryphe.iterable.CloseableIterable;
-import uk.gov.gchq.koryphe.iterable.CloseableIterator;
 
+import java.io.Closeable;
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.List;
@@ -51,7 +50,7 @@ private IterableUtil() {
      * @param <T>       the type of the items in the iterable
      * @return the lazily filtered iterable
      */
-    public static <T> CloseableIterable<T> filter(final Iterable<T> iterable, final Predicate predicate) {
+    public static <T> Iterable<T> filter(final Iterable<T> iterable, final Predicate predicate) {
         if (null == predicate) {
             throw new IllegalArgumentException("Predicate cannot be null");
         }
@@ -67,7 +66,7 @@ public static <T> CloseableIterable<T> filter(final Iterable<T> iterable, final
      * @param <T>        the type of the items in the iterable
      * @return the lazily filtered iterable
      */
-    public static <T> CloseableIterable<T> filter(final Iterable<T> iterable, final List<Predicate> predicates) {
+    public static <T> Iterable<T> filter(final Iterable<T> iterable, final List<Predicate> predicates) {
         if (null == iterable) {
             return null;
         }
@@ -84,14 +83,14 @@ public static <T> CloseableIterable<T> filter(final Iterable<T> iterable, final
         return new FilteredIterable<>(iterable, predicates);
     }
 
-    public static <I_ITEM, O_ITEM> CloseableIterable<O_ITEM> map(final Iterable<I_ITEM> iterable, final Function function) {
+    public static <I_ITEM, O_ITEM> Iterable<O_ITEM> map(final Iterable<I_ITEM> iterable, final Function function) {
         if (null == function) {
             throw new IllegalArgumentException("Function cannot be null");
         }
         return map(iterable, Collections.singletonList(function));
     }
 
-    public static <I_ITEM, O_ITEM> CloseableIterable<O_ITEM> map(final Iterable<I_ITEM> iterable, final List<Function> functions) {
+    public static <I_ITEM, O_ITEM> Iterable<O_ITEM> map(final Iterable<I_ITEM> iterable, final List<Function> functions) {
         if (null == iterable) {
             return null;
         }
@@ -108,21 +107,19 @@ public static <I_ITEM, O_ITEM> CloseableIterable<O_ITEM> map(final Iterable<I_IT
         return new MappedIterable<>(iterable, functions);
     }
 
-    public static <T> CloseableIterable<T> concat(final Iterable<? extends Iterable<? extends T>> iterables) {
+    public static <T> Iterable<T> concat(final Iterable<? extends Iterable<? extends T>> iterables) {
         return new ChainedIterable<>(iterables);
     }
 
-    public static <T> CloseableIterable<T> limit(final Iterable<T> iterable, final int start, final Integer end, final boolean truncate) {
+    public static <T> Iterable<T> limit(final Iterable<T> iterable, final int start, final Integer end, final boolean truncate) {
         return new LimitedIterable<>(iterable, start, end, truncate);
     }
 
     /**
      * @param <I_ITEM> input type of items in the input iterator
      * @param <O_ITEM> output type of items in the output iterator
-     * @deprecated Closable will be removed, it is used with scaling Big Data and does not belong in Koryphe.
      */
-    @Deprecated
-    private static class MappedIterable<I_ITEM, O_ITEM> implements CloseableIterable<O_ITEM> {
+    private static class MappedIterable<I_ITEM, O_ITEM> implements Closeable, Iterable<O_ITEM> {
         private final Iterable<I_ITEM> iterable;
         private final List<Function> functions;
 
@@ -132,7 +129,7 @@ private static class MappedIterable<I_ITEM, O_ITEM> implements CloseableIterable
         }
 
         @Override
-        public CloseableIterator<O_ITEM> iterator() {
+        public Iterator<O_ITEM> iterator() {
             return new MappedIterator<>(iterable.iterator(), functions);
         }
 
@@ -144,10 +141,8 @@ public void close() {
 
     /**
      * @param <O_ITEM> the type of items in the iterator
-     * @deprecated Closable will be removed, it is used with scaling Big Data and does not belong in Koryphe.
      */
-    @Deprecated
-    private static class MappedIterator<I_ITEM, O_ITEM> implements CloseableIterator<O_ITEM> {
+    private static class MappedIterator<I_ITEM, O_ITEM> implements Closeable, Iterator<O_ITEM> {
         private final Iterator<? extends I_ITEM> iterator;
         private final List<Function> functions;
 
@@ -182,10 +177,8 @@ public void close() {
 
     /**
      * @param <T> the type of items in the iterator
-     * @deprecated Closable will be removed, it is used with scaling Big Data and does not belong in Koryphe.
      */
-    @Deprecated
-    private static class FilteredIterable<T> implements CloseableIterable<T> {
+    private static class FilteredIterable<T> implements Closeable, Iterable<T> {
         private final Iterable<T> iterable;
         private final List<Predicate> predicates;
 
@@ -195,7 +188,7 @@ private static class FilteredIterable<T> implements CloseableIterable<T> {
         }
 
         @Override
-        public CloseableIterator<T> iterator() {
+        public Iterator<T> iterator() {
             return new FilteredIterator<>(iterable.iterator(), predicates);
         }
 
@@ -207,10 +200,8 @@ public void close() {
 
     /**
      * @param <T> the type of items in the iterator
-     * @deprecated Closable will be removed, it is used with scaling Big Data and does not belong in Koryphe.
      */
-    @Deprecated
-    private static class FilteredIterator<T> implements CloseableIterator<T> {
+    private static class FilteredIterator<T> implements Closeable, Iterator<T> {
         private final Iterator<? extends T> iterator;
         private final And<T> andPredicate;
 
@@ -271,10 +262,8 @@ public void close() {
 
     /**
      * @param <T> the type of items in the iterator
-     * @deprecated Closable will be removed, it is used with scaling Big Data and does not belong in Koryphe.
      */
-    @Deprecated
-    private static class ChainedIterable<T> implements CloseableIterable<T> {
+    private static class ChainedIterable<T> implements Closeable, Iterable<T> {
         private final Iterable<? extends Iterable<? extends T>> iterables;
 
         ChainedIterable(final Iterable<? extends Iterable<? extends T>> iterables) {
@@ -285,7 +274,7 @@ private static class ChainedIterable<T> implements CloseableIterable<T> {
         }
 
         @Override
-        public CloseableIterator<T> iterator() {
+        public Iterator<T> iterator() {
             return new ChainedIterator<>(iterables.iterator());
         }
 
@@ -299,10 +288,8 @@ public void close() {
 
     /**
      * @param <T> the type of items in the iterator
-     * @deprecated Closable will be removed, it is used with scaling Big Data and does not belong in Koryphe.
      */
-    @Deprecated
-    private static class ChainedIterator<T> implements CloseableIterator<T> {
+    private static class ChainedIterator<T> implements Closeable, Iterator<T> {
         private final Iterator<? extends Iterable<? extends T>> iterablesIterator;
         private Iterator<? extends T> currentIterator = Collections.emptyIterator();
 
@@ -349,10 +336,8 @@ private Iterator<? extends T> getIterator() {
 
     /**
      * @param <T> the type of items in the iterator
-     * @deprecated Closable will be removed, it is used with scaling Big Data and does not belong in Koryphe.
      */
-    @Deprecated
-    private static final class LimitedIterable<T> implements CloseableIterable<T> {
+    private static final class LimitedIterable<T> implements Closeable, Iterable<T> {
         private final Iterable<T> iterable;
         private final int start;
         private final Integer end;
@@ -386,17 +371,15 @@ public void close() {
         }
 
         @Override
-        public CloseableIterator<T> iterator() {
+        public Iterator<T> iterator() {
             return new LimitedIterator<>(iterable.iterator(), start, end, truncate);
         }
     }
 
     /**
      * @param <T> the type of items in the iterator
-     * @deprecated Closable will be removed, it is used with scaling Big Data and does not belong in Koryphe.
      */
-    @Deprecated
-    private static final class LimitedIterator<T> implements CloseableIterator<T> {
+    private static final class LimitedIterator<T> implements Closeable, Iterator<T> {
         private final Iterator<T> iterator;
         private final Integer end;
         private int index = 0;
diff --git a/core/src/test/java/uk/gov/gchq/koryphe/impl/function/ToDoubleTest.java b/core/src/test/java/uk/gov/gchq/koryphe/impl/function/ToDoubleTest.java
new file mode 100644
index 000000000..7b1310d39
--- /dev/null
+++ b/core/src/test/java/uk/gov/gchq/koryphe/impl/function/ToDoubleTest.java
@@ -0,0 +1,128 @@
+/*
+ * Copyright 2022 Crown Copyright
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package uk.gov.gchq.koryphe.impl.function;
+
+import org.junit.jupiter.api.Test;
+import uk.gov.gchq.koryphe.function.FunctionTest;
+import uk.gov.gchq.koryphe.util.JsonSerialiser;
+
+import java.io.IOException;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class ToDoubleTest extends FunctionTest<ToDouble> {
+
+    @Test
+    public void shouldThrowException() {
+        // Given
+        final ToDouble function = new ToDouble();
+
+        // When
+        Exception exception = assertThrows(IllegalArgumentException.class, () -> {
+            function.apply(true);
+        });
+
+        String expectedMessage = "Could not convert value to Double: ";
+        String actualMessage = exception.getMessage();
+
+        // Then
+        assertTrue(actualMessage.contains(expectedMessage));
+    }
+
+    @Test
+    public void shouldConvertStringToDouble() {
+        // Given
+        final ToDouble function = new ToDouble();
+
+        // When
+        Object output = function.apply("5.2");
+
+        // Then
+        assertEquals(5.2, output);
+        assertEquals(Double.class, output.getClass());
+    }
+
+    @Test
+    public void shouldConvertNumberToDouble() {
+        // Given
+        final ToDouble function = new ToDouble();
+
+        // When
+        Object output = function.apply(5);
+
+        // Then
+        assertEquals(5.0, output);
+        assertEquals(Double.class, output.getClass());
+    }
+
+    @Test
+    public void shouldReturnNullWhenValueIsNull() {
+        // Given
+        final ToDouble function = new ToDouble();
+
+        // When
+        final Object output = function.apply(null);
+
+        // Then
+        assertNull(output);
+    }
+
+    @Override
+    protected ToDouble getInstance() {
+        return new ToDouble();
+    }
+
+    @Override
+    protected Iterable<ToDouble> getDifferentInstancesOrNull() {
+        return null;
+    }
+
+    @Override
+    protected Class[] getExpectedSignatureInputClasses() {
+        return new Class[] { Object.class };
+    }
+
+    @Override
+    protected Class[] getExpectedSignatureOutputClasses() {
+        return new Class[] { Double.class };
+    }
+
+    @Test
+    @Override
+    public void shouldJsonSerialiseAndDeserialise() throws IOException {
+        // Given
+        final ToDouble function = new ToDouble();
+
+        // When
+        final String json = JsonSerialiser.serialise(function);
+
+        // Then
+        JsonSerialiser.assertEquals(String.format("{%n" +
+                "  \"class\" : \"uk.gov.gchq.koryphe.impl.function.ToDouble\"%n" +
+                "}"), json);
+
+        // When 2
+        final ToDouble deserialisedMethod = JsonSerialiser.deserialise(json, ToDouble.class);
+
+        // Then 2
+        assertNotNull(deserialisedMethod);
+    }
+}
diff --git a/core/src/test/java/uk/gov/gchq/koryphe/iterable/StreamIterableTest.java b/core/src/test/java/uk/gov/gchq/koryphe/iterable/StreamIterableTest.java
deleted file mode 100644
index 2ea4c0957..000000000
--- a/core/src/test/java/uk/gov/gchq/koryphe/iterable/StreamIterableTest.java
+++ /dev/null
@@ -1,48 +0,0 @@
-/*
- * Copyright 2019-2020 Crown Copyright
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package uk.gov.gchq.koryphe.iterable;
-
-import org.junit.jupiter.api.Test;
-
-import java.util.Iterator;
-import java.util.function.Supplier;
-import java.util.stream.Stream;
-
-import static org.mockito.BDDMockito.given;
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.verify;
-
-public class StreamIterableTest {
-
-    @Test
-    public void shouldDelegateIteratorToIterable() {
-        // Given
-        final Supplier<Stream<Object>> streamSupplier = mock(Supplier.class);
-        final Stream<Object> stream = mock(Stream.class);
-        given(streamSupplier.get()).willReturn(stream);
-        final StreamIterable<Object> wrappedIterable = new StreamIterable<>(streamSupplier);
-        final Iterator<Object> iterator = mock(Iterator.class);
-        given(stream.iterator()).willReturn(iterator);
-
-        // When
-        final CloseableIterator<Object> result = wrappedIterable.iterator();
-
-        // Then - call has next and check it was called on the mock.
-        result.hasNext();
-        verify(iterator).hasNext();
-    }
-}
diff --git a/core/src/test/java/uk/gov/gchq/koryphe/iterable/StreamIteratorTest.java b/core/src/test/java/uk/gov/gchq/koryphe/iterable/StreamIteratorTest.java
deleted file mode 100644
index f6ed613b8..000000000
--- a/core/src/test/java/uk/gov/gchq/koryphe/iterable/StreamIteratorTest.java
+++ /dev/null
@@ -1,40 +0,0 @@
-/*
- * Copyright 2019-2020 Crown Copyright
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package uk.gov.gchq.koryphe.iterable;
-
-import org.junit.jupiter.api.Test;
-
-import java.util.stream.Stream;
-
-import static org.mockito.Mockito.mock;
-import static org.mockito.Mockito.verify;
-
-public class StreamIteratorTest {
-
-    @Test
-    public void shouldDelegateCloseToWrappedIterator() {
-        // Given
-        final Stream<Object> stream = mock(Stream.class);
-        final StreamIterator<Object> streamIterator = new StreamIterator<>(stream);
-
-        // When
-        streamIterator.close();
-
-        // Then
-        verify(stream).close();
-    }
-}
diff --git a/core/src/test/java/uk/gov/gchq/koryphe/tuple/binaryoperator/TupleAdaptedBinaryOperatorCompositeTest.java b/core/src/test/java/uk/gov/gchq/koryphe/tuple/binaryoperator/TupleAdaptedBinaryOperatorCompositeTest.java
index 4452f14f6..71dc37a09 100644
--- a/core/src/test/java/uk/gov/gchq/koryphe/tuple/binaryoperator/TupleAdaptedBinaryOperatorCompositeTest.java
+++ b/core/src/test/java/uk/gov/gchq/koryphe/tuple/binaryoperator/TupleAdaptedBinaryOperatorCompositeTest.java
@@ -15,15 +15,18 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
-import static org.junit.jupiter.api.Assertions.fail;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+public class TupleAdaptedBinaryOperatorCompositeTest
+        extends BinaryOperatorTest<TupleAdaptedBinaryOperatorComposite<Object>> {
 
-public class TupleAdaptedBinaryOperatorCompositeTest extends BinaryOperatorTest<TupleAdaptedBinaryOperatorComposite> {
     @Test
     @Override
+    @SuppressWarnings("unchecked")
     public void shouldJsonSerialiseAndDeserialise() throws IOException {
         // Given
-        TupleAdaptedBinaryOperatorComposite instance = getInstance();
-        String json = "" +
+        final TupleAdaptedBinaryOperatorComposite<Object> instance = getInstance();
+        final String json = "" +
                 "{" +
                     "\"operators\": [" +
                         "{" +
@@ -36,8 +39,9 @@ public void shouldJsonSerialiseAndDeserialise() throws IOException {
                 "}";
 
         // When
-        String serialised = JsonSerialiser.serialise(instance);
-        TupleAdaptedBinaryOperatorComposite deserialised = JsonSerialiser.deserialise(json, TupleAdaptedBinaryOperatorComposite.class);
+        final String serialised = JsonSerialiser.serialise(instance);
+        final TupleAdaptedBinaryOperatorComposite<Object> deserialised = JsonSerialiser.deserialise(json,
+                TupleAdaptedBinaryOperatorComposite.class);
 
         // Then
         JsonSerialiser.assertEquals(json, serialised);
@@ -46,43 +50,42 @@ public void shouldJsonSerialiseAndDeserialise() throws IOException {
     }
 
     @Override
-    protected TupleAdaptedBinaryOperatorComposite getInstance() {
-        return new TupleAdaptedBinaryOperatorComposite.Builder()
+    protected TupleAdaptedBinaryOperatorComposite<Object> getInstance() {
+        return new TupleAdaptedBinaryOperatorComposite.Builder<>()
                 .select(new String[] { "input", "anotherInput" })
                 .execute(new Sum())
                 .build();
     }
 
     @Override
-    protected Iterable<TupleAdaptedBinaryOperatorComposite> getDifferentInstancesOrNull() {
+    protected Iterable<TupleAdaptedBinaryOperatorComposite<Object>> getDifferentInstancesOrNull() {
         return Arrays.asList(
-                new TupleAdaptedBinaryOperatorComposite.Builder()
+                new TupleAdaptedBinaryOperatorComposite.Builder<>()
                         .select(new String[] { "differentInput", "anotherInput" })
                         .execute(new Sum())
                         .build(),
-                new TupleAdaptedBinaryOperatorComposite.Builder()
+                new TupleAdaptedBinaryOperatorComposite.Builder<>()
                         .select(new String[] { "input", "anotherInput" })
                         .execute(new Product())
                         .build(),
-                new TupleAdaptedBinaryOperatorComposite(),
-                new TupleAdaptedBinaryOperatorComposite.Builder()
+                new TupleAdaptedBinaryOperatorComposite<>(),
+                new TupleAdaptedBinaryOperatorComposite.Builder<>()
                         .select(new String[] { "input", "anotherInput" })
                         .execute(new Sum())
-                        .select(new String[] { "input", "differentInput"})
+                        .select(new String[] { "input", "differentInput" })
                         .execute(new Max())
-                .build()
-        );
+                        .build());
     }
 
     @Test
     public void shouldErrorIfObjectsAreTheWrongType() {
         // Given
-        ArrayTuple stateTuple = new ArrayTuple(5, 10, 15);
-        ArrayTuple inputTuple = new ArrayTuple(1, "two", 3);
+        final ArrayTuple stateTuple = new ArrayTuple(5, 10, 15);
+        final ArrayTuple inputTuple = new ArrayTuple(1, "two", 3);
 
         // When
-        TupleAdaptedBinaryOperatorComposite<Integer> boc = new TupleAdaptedBinaryOperatorComposite.Builder<Integer>()
-                .select(new Integer[]{ 0 })
+        final TupleAdaptedBinaryOperatorComposite<Integer> boc = new TupleAdaptedBinaryOperatorComposite.Builder<Integer>()
+                .select(new Integer[] { 0 })
                 .execute(new Product())
                 .select(new Integer[] { 1 })
                 .execute(new Max())
@@ -91,24 +94,20 @@ public void shouldErrorIfObjectsAreTheWrongType() {
                 .build();
 
         // Then
-        try {
-            boc.apply(stateTuple, inputTuple);
-            fail("Expected aggregation to fail");
-        } catch (ClassCastException e) {
-            assertNotNull(e.getMessage());
-        }
-
+        final ClassCastException actual = assertThrows(ClassCastException.class,
+                () -> boc.apply(stateTuple, inputTuple));
+        assertNotNull(actual.getMessage());
     }
 
     @Test
     public void shouldMergeTheInputTupleIntoTheStateTuple() {
         // Given
-        ArrayTuple stateTuple = new ArrayTuple(5, 10, 15);
-        ArrayTuple inputTuple = new ArrayTuple(1, 2, 3);
+        final ArrayTuple stateTuple = new ArrayTuple(5, 10, 15);
+        final ArrayTuple inputTuple = new ArrayTuple(1, 2, 3);
 
         // When
-        TupleAdaptedBinaryOperatorComposite<Integer> boc = new TupleAdaptedBinaryOperatorComposite.Builder<Integer>()
-                .select(new Integer[]{ 0 })
+        final TupleAdaptedBinaryOperatorComposite<Integer> boc = new TupleAdaptedBinaryOperatorComposite.Builder<Integer>()
+                .select(new Integer[] { 0 })
                 .execute(new Product())
                 .select(new Integer[] { 1 })
                 .execute(new Max())
@@ -116,13 +115,11 @@ public void shouldMergeTheInputTupleIntoTheStateTuple() {
                 .execute(new Sum())
                 .build();
 
-        Tuple<Integer> agg = boc.apply(stateTuple, inputTuple);
+        final Tuple<Integer> agg = boc.apply(stateTuple, inputTuple);
 
         // Then
         assertEquals(5, agg.get(0));
         assertEquals(10, agg.get(1));
         assertEquals(18, agg.get(2));
     }
-
-
 }
\ No newline at end of file
diff --git a/core/src/test/java/uk/gov/gchq/koryphe/util/IterableUtilTest.java b/core/src/test/java/uk/gov/gchq/koryphe/util/IterableUtilTest.java
index 71067e61d..b87ff6f04 100644
--- a/core/src/test/java/uk/gov/gchq/koryphe/util/IterableUtilTest.java
+++ b/core/src/test/java/uk/gov/gchq/koryphe/util/IterableUtilTest.java
@@ -19,8 +19,6 @@
 import com.google.common.collect.Lists;
 import org.junit.jupiter.api.Test;
 
-import uk.gov.gchq.koryphe.iterable.CloseableIterable;
-
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
@@ -112,7 +110,7 @@ public void shouldLimitResultsToFirstItem() {
         final int end = 1;
 
         // When
-        final CloseableIterable<Integer> limitedValues = IterableUtil.limit(values, start, end, true);
+        final Iterable<Integer> limitedValues = IterableUtil.limit(values, start, end, true);
 
         // Then
         assertEquals(values.subList(start, end), Lists.newArrayList(limitedValues));
@@ -126,7 +124,7 @@ public void shouldLimitResultsToLastItem() {
         final int end = Integer.MAX_VALUE;
 
         // When
-        final CloseableIterable<Integer> limitedValues = IterableUtil.limit(values, start, end, true);
+        final Iterable<Integer> limitedValues = IterableUtil.limit(values, start, end, true);
 
         // Then
         assertEquals(values.subList(start, values.size()), Lists.newArrayList(limitedValues));
@@ -140,7 +138,7 @@ public void shouldNotLimitResults() {
         final int end = Integer.MAX_VALUE;
 
         // When
-        final CloseableIterable<Integer> limitedValues = IterableUtil.limit(values, start, end, true);
+        final Iterable<Integer> limitedValues = IterableUtil.limit(values, start, end, true);
 
         // Then
         assertEquals(values, Lists.newArrayList(limitedValues));
@@ -154,7 +152,7 @@ public void shouldReturnNoValuesIfStartIsBiggerThanSize() {
         final int end = Integer.MAX_VALUE;
 
         // When
-        final CloseableIterable<Integer> limitedValues = IterableUtil.limit(values, start, end, true);
+        final Iterable<Integer> limitedValues = IterableUtil.limit(values, start, end, true);
 
         // Then
         assertTrue(Lists.newArrayList(limitedValues).isEmpty());
@@ -183,7 +181,7 @@ public void shouldThrowExceptionIfDataIsTruncated() {
         final boolean truncate = false;
 
         // When
-        final CloseableIterable<Integer> limitedValues = IterableUtil.limit(values, start, end, truncate);
+        final Iterable<Integer> limitedValues = IterableUtil.limit(values, start, end, truncate);
 
         // Then
         final Exception exception = assertThrows(NoSuchElementException.class, () -> {
@@ -197,7 +195,7 @@ public void shouldThrowExceptionIfDataIsTruncated() {
     @Test
     public void shouldHandleNullIterable() {
         // Given
-        final CloseableIterable<Integer> nullIterable = IterableUtil.limit(null, 0, 1, true);
+        final Iterable<Integer> nullIterable = IterableUtil.limit(null, 0, 1, true);
 
         // Then
         assertTrue(Lists.newArrayList(nullIterable).isEmpty());
@@ -212,7 +210,7 @@ public void shouldHandleLimitEqualToIterableLength() {
         final boolean truncate = false;
 
         // When
-        final CloseableIterable<Integer> equalValues = IterableUtil.limit(values, start, end, truncate);
+        final Iterable<Integer> equalValues = IterableUtil.limit(values, start, end, truncate);
 
         // Then
         assertEquals(values, Lists.newArrayList(equalValues));