diff --git a/client/src/main/kotlin/com/r3corda/client/fxutils/FlattenedList.kt b/client/src/main/kotlin/com/r3corda/client/fxutils/FlattenedList.kt
index b048c173dc..a417fa8e8f 100644
--- a/client/src/main/kotlin/com/r3corda/client/fxutils/FlattenedList.kt
+++ b/client/src/main/kotlin/com/r3corda/client/fxutils/FlattenedList.kt
@@ -1,10 +1,12 @@
 package com.r3corda.client.fxutils
 
 import javafx.beans.InvalidationListener
+import javafx.beans.value.ChangeListener
 import javafx.beans.value.ObservableValue
 import javafx.collections.ListChangeListener
 import javafx.collections.ObservableList
 import javafx.collections.transformation.TransformationList
+import org.eclipse.jetty.server.Authentication
 import java.util.*
 
 /**
@@ -20,21 +22,30 @@ class FlattenedList<A>(val sourceList: ObservableList<out ObservableValue<out A>
      *
      * Note that because of the bookkeeping required for this map, any remove operation and any add operation that
      * inserts to the middle of the list will be O(N) as we need to scan the map and shift indices accordingly.
+     *
+     * Note also that we're wrapping each ObservableValue, this is required because we want to support reusing of
+     * ObservableValues and we need each to have a different hash.
      */
-    val indexMap = HashMap<ObservableValue<out A>, Pair<Int, InvalidationListener>>()
+    class WrappedObservableValue<A>(
+            val observableValue: ObservableValue<A>
+    )
+    val indexMap = HashMap<WrappedObservableValue<out A>, Pair<Int, ChangeListener<A>>>()
     init {
         sourceList.forEachIndexed { index, observableValue ->
-            indexMap[observableValue] = Pair(index, createListener(observableValue))
+            val wrappedObservableValue = WrappedObservableValue(observableValue)
+            indexMap[wrappedObservableValue] = Pair(index, createListener(wrappedObservableValue))
         }
     }
 
-    private fun createListener(observableValue: ObservableValue<out A>): InvalidationListener {
-        return InvalidationListener {
-            val currentIndex = indexMap[observableValue]!!.first
+    private fun createListener(wrapped: WrappedObservableValue<out A>): ChangeListener<A> {
+        val listener = ChangeListener<A> { _observableValue, oldValue, newValue ->
+            val currentIndex = indexMap[wrapped]!!.first
             beginChange()
-            nextAdd(currentIndex, currentIndex + 1)
+            nextReplace(currentIndex, currentIndex + 1, listOf(oldValue))
             endChange()
         }
+        wrapped.observableValue.addListener(listener)
+        return listener
     }
 
     override fun sourceChanged(c: ListChangeListener.Change<out ObservableValue<out A>>) {
@@ -51,17 +62,17 @@ class FlattenedList<A>(val sourceList: ObservableList<out ObservableValue<out A>
             } else {
                 val removed = c.removed
                 if (removed.size != 0) {
-                    val removeStart = indexMap[removed.first()]!!.first
-                    val removeEnd = indexMap[removed.last()]!!.first + 1
-                    require(removeStart < removeEnd)
-                    val removeRange = removeEnd - removeStart
+                    // TODO this assumes that if wasAdded() == true then we are adding elements to the getFrom() position
+                    val removeStart = c.from
+                    val removeRange = c.removed.size
+                    val removeEnd = c.from + removeRange
                     val iterator = indexMap.iterator()
                     for (entry in iterator) {
-                        val (observableValue, pair) = entry
+                        val (wrapped, pair) = entry
                         val (index, listener) = pair
                         if (index >= removeStart) {
                             if (index < removeEnd) {
-                                observableValue.removeListener(listener)
+                                wrapped.observableValue.removeListener(listener)
                                 iterator.remove()
                             } else {
                                 // Shift indices
@@ -87,7 +98,8 @@ class FlattenedList<A>(val sourceList: ObservableList<out ObservableValue<out A>
                         }
                     }
                     c.addedSubList.forEachIndexed { sublistIndex, observableValue ->
-                        indexMap[observableValue] = Pair(addStart + sublistIndex, createListener(observableValue))
+                        val wrapped = WrappedObservableValue(observableValue)
+                        indexMap[wrapped] = Pair(addStart + sublistIndex, createListener(wrapped))
                     }
                     nextAdd(addStart, addEnd)
                 }
diff --git a/client/src/test/kotlin/com/r3corda/client/fxutils/FlattenedListTest.kt b/client/src/test/kotlin/com/r3corda/client/fxutils/FlattenedListTest.kt
index 8c5cd1b714..646418b3ae 100644
--- a/client/src/test/kotlin/com/r3corda/client/fxutils/FlattenedListTest.kt
+++ b/client/src/test/kotlin/com/r3corda/client/fxutils/FlattenedListTest.kt
@@ -9,81 +9,105 @@ class FlattenedListTest {
 
     var sourceList = FXCollections.observableArrayList(SimpleObjectProperty(1234))
     var flattenedList = FlattenedList(sourceList)
+    var replayedList = ReplayedList(flattenedList)
 
     @Before
     fun setup() {
         sourceList = FXCollections.observableArrayList(SimpleObjectProperty(1234))
         flattenedList = FlattenedList(sourceList)
+        replayedList = ReplayedList(flattenedList)
     }
 
     @Test
     fun addWorks() {
-        require(flattenedList.size == 1)
-        require(flattenedList[0] == 1234)
+        require(replayedList.size == 1)
+        require(replayedList[0] == 1234)
 
         sourceList.add(SimpleObjectProperty(12))
-        require(flattenedList.size == 2)
-        require(flattenedList[0] == 1234)
-        require(flattenedList[1] == 12)
+        require(replayedList.size == 2)
+        require(replayedList[0] == 1234)
+        require(replayedList[1] == 12)
 
         sourceList.add(SimpleObjectProperty(34))
-        require(flattenedList.size == 3)
-        require(flattenedList[0] == 1234)
-        require(flattenedList[1] == 12)
-        require(flattenedList[2] == 34)
+        require(replayedList.size == 3)
+        require(replayedList[0] == 1234)
+        require(replayedList[1] == 12)
+        require(replayedList[2] == 34)
 
         sourceList.add(0, SimpleObjectProperty(56))
-        require(flattenedList.size == 4)
-        require(flattenedList[0] == 56)
-        require(flattenedList[1] == 1234)
-        require(flattenedList[2] == 12)
-        require(flattenedList[3] == 34)
+        require(replayedList.size == 4)
+        require(replayedList[0] == 56)
+        require(replayedList[1] == 1234)
+        require(replayedList[2] == 12)
+        require(replayedList[3] == 34)
 
         sourceList.addAll(2, listOf(SimpleObjectProperty(78), SimpleObjectProperty(910)))
-        require(flattenedList.size == 6)
-        require(flattenedList[0] == 56)
-        require(flattenedList[1] == 1234)
-        require(flattenedList[2] == 78)
-        require(flattenedList[3] == 910)
-        require(flattenedList[4] == 12)
-        require(flattenedList[5] == 34)
+        require(replayedList.size == 6)
+        require(replayedList[0] == 56)
+        require(replayedList[1] == 1234)
+        require(replayedList[2] == 78)
+        require(replayedList[3] == 910)
+        require(replayedList[4] == 12)
+        require(replayedList[5] == 34)
     }
 
     @Test
     fun removeWorks() {
         val firstRemoved = sourceList.removeAt(0)
         require(firstRemoved.get() == 1234)
-        require(flattenedList.size == 0)
+        require(replayedList.size == 0)
         firstRemoved.set(123)
 
         sourceList.add(SimpleObjectProperty(12))
         sourceList.add(SimpleObjectProperty(34))
         sourceList.add(SimpleObjectProperty(56))
-        require(flattenedList.size == 3)
+        require(replayedList.size == 3)
         val secondRemoved = sourceList.removeAt(1)
         require(secondRemoved.get() == 34)
-        require(flattenedList.size == 2)
-        require(flattenedList[0] == 12)
-        require(flattenedList[1] == 56)
+        require(replayedList.size == 2)
+        require(replayedList[0] == 12)
+        require(replayedList[1] == 56)
         secondRemoved.set(123)
 
         sourceList.clear()
-        require(flattenedList.size == 0)
+        require(replayedList.size == 0)
     }
 
     @Test
     fun updatingObservableWorks() {
-        require(flattenedList[0] == 1234)
+        require(replayedList[0] == 1234)
         sourceList[0].set(4321)
-        require(flattenedList[0] == 4321)
+        require(replayedList[0] == 4321)
 
         sourceList.add(0, SimpleObjectProperty(12))
         sourceList[1].set(8765)
-        require(flattenedList[0] == 12)
-        require(flattenedList[1] == 8765)
+        require(replayedList[0] == 12)
+        require(replayedList[1] == 8765)
 
         sourceList[0].set(34)
-        require(flattenedList[0] == 34)
-        require(flattenedList[1] == 8765)
+        require(replayedList[0] == 34)
+        require(replayedList[1] == 8765)
+    }
+
+    @Test
+    fun reusingObservableWorks() {
+        val observable = SimpleObjectProperty(12)
+        sourceList.add(observable)
+        sourceList.add(observable)
+        require(replayedList.size == 3)
+        require(replayedList[0] == 1234)
+        require(replayedList[1] == 12)
+        require(replayedList[2] == 12)
+
+        observable.set(34)
+        require(replayedList.size == 3)
+        require(replayedList[0] == 1234)
+        require(replayedList[1] == 34)
+        require(replayedList[2] == 34)
+
+        sourceList.removeAt(1)
+        require(replayedList.size == 2)
+        require(replayedList[0] == 1234)
+        require(replayedList[1] == 34)
     }
 }
diff --git a/client/src/test/kotlin/com/r3corda/client/fxutils/ReplayedList.kt b/client/src/test/kotlin/com/r3corda/client/fxutils/ReplayedList.kt
new file mode 100644
index 0000000000..c9b828e9ab
--- /dev/null
+++ b/client/src/test/kotlin/com/r3corda/client/fxutils/ReplayedList.kt
@@ -0,0 +1,63 @@
+package com.r3corda.client.fxutils
+
+import javafx.collections.ListChangeListener
+import javafx.collections.ObservableList
+import javafx.collections.transformation.TransformationList
+import java.util.*
+
+/**
+ * This list type just replays changes propagated from the underlying source list. Used for testing changes.
+ */
+class ReplayedList<A>(sourceList: ObservableList<A>) : TransformationList<A, A>(sourceList) {
+
+    val replayedList = ArrayList<A>(sourceList)
+
+    override val size: Int get() = replayedList.size
+
+    override fun sourceChanged(c: ListChangeListener.Change<out A>) {
+
+        beginChange()
+        while (c.next()) {
+            if (c.wasPermutated()) {
+                val from = c.from
+                val to = c.to
+                val permutation = IntArray(to, { c.getPermutation(it) })
+                val permutedSubList = ArrayList<A>(to - from)
+                for (i in 0 .. (to - from - 1)) {
+                    permutedSubList.add(replayedList[permutation[from + i]])
+                }
+                permutedSubList.forEachIndexed { i, element ->
+                    replayedList[from + i] = element
+                }
+                nextPermutation(from, to, permutation)
+            } else if (c.wasUpdated()) {
+                for (i in c.from .. c.to - 1) {
+                    replayedList[i] = c.list[i]
+                    nextUpdate(i)
+                }
+            } else {
+                if (c.wasRemoved()) {
+                    // TODO this assumes that if wasAdded() == true then we are adding elements to the getFrom() position
+                    val removePosition = c.from
+                    for (i in 0 .. c.removedSize - 1) {
+                        replayedList.removeAt(removePosition)
+                    }
+                    nextRemove(c.from, c.removed)
+                }
+                if (c.wasAdded()) {
+                    val addStart = c.from
+                    val addEnd = c.to
+                    for (i in addStart .. addEnd - 1) {
+                        replayedList.add(i, c.list[i])
+                    }
+                    nextAdd(addStart, addEnd)
+                }
+            }
+        }
+        endChange()
+    }
+
+    override fun getSourceIndex(index: Int) = index
+
+    override fun get(index: Int) = replayedList[index]
+}
diff --git a/client/src/test/kotlin/com/r3corda/client/fxutils/ReplayedListTest.kt b/client/src/test/kotlin/com/r3corda/client/fxutils/ReplayedListTest.kt
new file mode 100644
index 0000000000..e0653eeb2e
--- /dev/null
+++ b/client/src/test/kotlin/com/r3corda/client/fxutils/ReplayedListTest.kt
@@ -0,0 +1,86 @@
+package com.r3corda.client.fxutils
+
+import javafx.collections.FXCollections
+import org.junit.Before
+import org.junit.Test
+
+class ReplayedListTest {
+
+    var sourceList = FXCollections.observableArrayList(1234)
+    var replayedList = ReplayedList(sourceList)
+
+    @Before
+    fun setup() {
+        sourceList = FXCollections.observableArrayList(1234)
+        replayedList = ReplayedList(sourceList)
+    }
+
+    @Test
+    fun addWorks() {
+        require(replayedList.size == 1)
+        require(replayedList[0] == 1234)
+
+        sourceList.add(12)
+        require(replayedList.size == 2)
+        require(replayedList[0] == 1234)
+        require(replayedList[1] == 12)
+
+        sourceList.add(34)
+        require(replayedList.size == 3)
+        require(replayedList[0] == 1234)
+        require(replayedList[1] == 12)
+        require(replayedList[2] == 34)
+
+        sourceList.add(0, 56)
+        require(replayedList.size == 4)
+        require(replayedList[0] == 56)
+        require(replayedList[1] == 1234)
+        require(replayedList[2] == 12)
+        require(replayedList[3] == 34)
+
+        sourceList.addAll(2, listOf(78, 910))
+        require(replayedList.size == 6)
+        require(replayedList[0] == 56)
+        require(replayedList[1] == 1234)
+        require(replayedList[2] == 78)
+        require(replayedList[3] == 910)
+        require(replayedList[4] == 12)
+        require(replayedList[5] == 34)
+    }
+
+    @Test
+    fun removeWorks() {
+        val firstRemoved = sourceList.removeAt(0)
+        require(firstRemoved == 1234)
+        require(replayedList.size == 0)
+
+        sourceList.add(12)
+        sourceList.add(34)
+        sourceList.add(56)
+        require(replayedList.size == 3)
+        val secondRemoved = sourceList.removeAt(1)
+        require(secondRemoved == 34)
+        require(replayedList.size == 2)
+        require(replayedList[0] == 12)
+        require(replayedList[1] == 56)
+
+        sourceList.clear()
+        require(replayedList.size == 0)
+    }
+
+    @Test
+    fun updateWorks() {
+        require(replayedList[0] == 1234)
+        sourceList[0] = 4321
+        require(replayedList[0] == 4321)
+
+        sourceList.add(0, 12)
+        sourceList[1] = 8765
+        require(replayedList[0] == 12)
+        require(replayedList[1] == 8765)
+
+        sourceList[0] = 34
+        require(replayedList[0] == 34)
+        require(replayedList[1] == 8765)
+    }
+}