diff --git a/src/observable/list/MappedList.js b/src/observable/list/MappedList.js
index 139a6e73..0bc4065a 100644
--- a/src/observable/list/MappedList.js
+++ b/src/observable/list/MappedList.js
@@ -1,5 +1,6 @@
 /*
 Copyright 2020 Bruno Windels <bruno@windels.cloud>
+Copyright 2021 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -17,11 +18,12 @@ limitations under the License.
 import {BaseObservableList} from "./BaseObservableList.js";
 
 export class MappedList extends BaseObservableList {
-    constructor(sourceList, mapper, updater) {
+    constructor(sourceList, mapper, updater, removeCallback) {
         super();
         this._sourceList = sourceList;
         this._mapper = mapper;
         this._updater = updater;
+        this._removeCallback = removeCallback;
         this._sourceUnsubscribe = null;
         this._mappedValues = null;
     }
@@ -56,6 +58,9 @@ export class MappedList extends BaseObservableList {
     onRemove(index) {
         const mappedValue = this._mappedValues[index];
         this._mappedValues.splice(index, 1);
+        if (this._removeCallback) {
+            this._removeCallback(mappedValue);
+        }
         this.emitRemove(index, mappedValue);
     }
 
@@ -70,6 +75,21 @@ export class MappedList extends BaseObservableList {
         this._sourceUnsubscribe();
     }
 
+    findAndUpdate(predicate, updater) {
+        const index = this._mappedValues.findIndex(predicate);
+        if (index !== -1) {
+            const mappedValue = this._mappedValues[index];
+            // allow bailing out of sending an emit if updater determined its not needed
+            const params = updater(mappedValue);
+            if (params !== false) {
+                this.emitUpdate(index, mappedValue, params);
+            }
+            // found
+            return true;
+        }
+        return false;
+    }
+
     get length() {
         return this._mappedValues.length;
     }
@@ -79,6 +99,8 @@ export class MappedList extends BaseObservableList {
     }
 }
 
+import {ObservableArray} from "./ObservableArray.js";
+
 export async function tests() {
     class MockList extends BaseObservableList {
         get length() {
@@ -126,6 +148,59 @@ export async function tests() {
             source.emitUpdate(0, 7);
             assert(fired);
             unsubscribe();
-        }
+        },
+        "test findAndUpdate not found": assert => {
+            const source = new ObservableArray([1, 3, 4]);
+            const mapped = new MappedList(
+                source,
+                n => {return n*n;}
+            );
+            mapped.subscribe({
+                onUpdate() { assert.fail(); }
+            });
+            assert.equal(mapped.findAndUpdate(
+                n => n === 100,
+                () => assert.fail()
+            ), false);
+        },
+        "test findAndUpdate found but updater bails out of update": assert => {
+            const source = new ObservableArray([1, 3, 4]);
+            const mapped = new MappedList(
+                source,
+                n => {return n*n;}
+            );
+            mapped.subscribe({
+                onUpdate() { assert.fail(); }
+            });
+            let fired = false;
+            assert.equal(mapped.findAndUpdate(
+                n => n === 9,
+                n => {
+                    assert.equal(n, 9);
+                    fired = true;
+                    return false;
+                }
+            ), true);
+            assert.equal(fired, true);
+        },
+        "test findAndUpdate emits update": assert => {
+            const source = new ObservableArray([1, 3, 4]);
+            const mapped = new MappedList(
+                source,
+                n => {return n*n;}
+            );
+            let fired = false;
+            mapped.subscribe({
+                onUpdate(idx, n, params) {
+                    assert.equal(idx, 1);
+                    assert.equal(n, 9);
+                    assert.equal(params, "param");
+                    fired = true;
+                }
+            });
+            assert.equal(mapped.findAndUpdate(n => n === 9, () => "param"), true);
+            assert.equal(fired, true);
+        },
+        
     };
 }