diff --git a/src/customisations/Media.ts b/src/customisations/Media.ts
new file mode 100644
index 0000000000..27abc6bc50
--- /dev/null
+++ b/src/customisations/Media.ts
@@ -0,0 +1,138 @@
+/*
+ * 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.
+ * 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.
+ */
+
+import {MatrixClientPeg} from "../MatrixClientPeg";
+import {IMediaEventContent, IPreparedMedia, prepEventContentAsMedia} from "./models/IMediaEventContent";
+
+// Populate this class with the details of your customisations when copying it.
+
+// Implementation note: The Media class must complete the contract as shown here, though
+// the constructor can be whatever is relevant to your implementation. The mediaForX
+// functions below create an instance of the Media class and are used throughout the
+// project.
+
+/**
+ * A media object is a representation of a "source media" and an optional
+ * "thumbnail media", derived from event contents or external sources.
+ */
+export class Media {
+    // Per above, this constructor signature can be whatever is helpful for you.
+    constructor(private prepared: IPreparedMedia) {
+    }
+
+    /**
+     * The MXC URI of the source media.
+     */
+    public get srcMxc(): string {
+        return this.prepared.mxc;
+    }
+
+    /**
+     * The MXC URI of the thumbnail media, if a thumbnail is recorded. Null/undefined
+     * otherwise.
+     */
+    public get thumbnailMxc(): string | undefined | null {
+        return this.prepared.thumbnail?.mxc;
+    }
+
+    /**
+     * Whether or not a thumbnail is recorded for this media.
+     */
+    public get hasThumbnail(): boolean {
+        return !!this.thumbnailMxc;
+    }
+
+    /**
+     * The HTTP URL for the source media.
+     */
+    public get srcHttp(): string {
+        return MatrixClientPeg.get().mxcUrlToHttp(this.srcMxc);
+    }
+
+    /**
+     * Gets the HTTP URL for the thumbnail media with the requested characteristics, if a thumbnail
+     * is recorded for this media. Returns null/undefined otherwise.
+     * @param {number} width The desired width of the thumbnail.
+     * @param {number} height The desired height of the thumbnail.
+     * @param {"scale"|"crop"} mode The desired thumbnailing mode. Defaults to scale.
+     * @returns {string} The HTTP URL which points to the thumbnail.
+     */
+    public getThumbnailHttp(width: number, height: number, mode: 'scale' | 'crop' = "scale"): string | null | undefined {
+        if (!this.hasThumbnail) return null;
+        return MatrixClientPeg.get().mxcUrlToHttp(this.thumbnailMxc, width, height, mode);
+    }
+
+    /**
+     * Gets the HTTP URL for a thumbnail of the source media with the requested characteristics.
+     * @param {number} width The desired width of the thumbnail.
+     * @param {number} height The desired height of the thumbnail.
+     * @param {"scale"|"crop"} mode The desired thumbnailing mode. Defaults to scale.
+     * @returns {string} The HTTP URL which points to the thumbnail.
+     */
+    public getThumbnailOfSourceHttp(width: number, height: number, mode: 'scale' | 'crop' = "scale"): string {
+        return MatrixClientPeg.get().mxcUrlToHttp(this.srcMxc, width, height, mode);
+    }
+
+    /**
+     * Downloads the source media.
+     * @returns {Promise<Response>} Resolves to the server's response for chaining.
+     */
+    public downloadSource(): Promise<Response> {
+        return fetch(this.srcHttp);
+    }
+
+    /**
+     * Downloads the thumbnail media with the requested characteristics. If no thumbnail media is present,
+     * this throws an exception.
+     * @param {number} width The desired width of the thumbnail.
+     * @param {number} height The desired height of the thumbnail.
+     * @param {"scale"|"crop"} mode The desired thumbnailing mode. Defaults to scale.
+     * @returns {Promise<Response>} Resolves to the server's response for chaining.
+     */
+    public downloadThumbnail(width: number, height: number, mode: 'scale' | 'crop' = "scale"): Promise<Response> {
+        if (!this.hasThumbnail) throw new Error("Cannot download non-existent thumbnail");
+        return fetch(this.getThumbnailHttp(width, height, mode));
+    }
+
+    /**
+     * Downloads a thumbnail of the source media with the requested characteristics.
+     * @param {number} width The desired width of the thumbnail.
+     * @param {number} height The desired height of the thumbnail.
+     * @param {"scale"|"crop"} mode The desired thumbnailing mode. Defaults to scale.
+     * @returns {Promise<Response>} Resolves to the server's response for chaining.
+     */
+    public downloadThumbnailOfSource(width: number, height: number, mode: 'scale' | 'crop' = "scale"): Promise<Response> {
+        return fetch(this.getThumbnailOfSourceHttp(width, height, mode));
+    }
+}
+
+/**
+ * Creates a media object from event content.
+ * @param {IMediaEventContent} content The event content.
+ * @returns {Media} The media object.
+ */
+export function mediaFromContent(content: IMediaEventContent): Media {
+    return new Media(prepEventContentAsMedia(content));
+}
+
+/**
+ * Creates a media object from an MXC URI.
+ * @param {string} mxc The MXC URI.
+ * @returns {Media} The media object.
+ */
+export function mediaFromMxc(mxc: string): Media {
+    return mediaFromContent({url: mxc});
+}
diff --git a/src/customisations/models/IMediaEventContent.ts b/src/customisations/models/IMediaEventContent.ts
new file mode 100644
index 0000000000..0211a63787
--- /dev/null
+++ b/src/customisations/models/IMediaEventContent.ts
@@ -0,0 +1,87 @@
+/*
+ * 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.
+ * 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.
+ */
+
+// TODO: These types should be elsewhere.
+
+export interface IEncryptedFile {
+    url: string;
+    key: {
+        alg: string;
+        key_ops: string[];
+        kty: string;
+        k: string;
+        ext: boolean;
+    };
+    iv: string;
+    hashes: {[alg: string]: string};
+    v: string;
+}
+
+export interface IMediaEventContent {
+    url?: string; // required on unencrypted media
+    file?: IEncryptedFile; // required for *encrypted* media
+    info?: {
+        thumbnail_url?: string;
+        thumbnail_file?: IEncryptedFile;
+    };
+}
+
+export interface IPreparedMedia extends IMediaObject {
+    thumbnail?: IMediaObject;
+}
+
+export interface IMediaObject {
+    mxc: string;
+    file?: IEncryptedFile;
+}
+
+/**
+ * Parses an event content body into a prepared media object. This prepared media object
+ * can be used with other functions to manipulate the media.
+ * @param {IMediaEventContent} content Unredacted media event content. See interface.
+ * @returns {IPreparedMedia} A prepared media object.
+ * @throws Throws if the given content cannot be packaged into a prepared media object.
+ */
+export function prepEventContentAsMedia(content: IMediaEventContent): IPreparedMedia {
+    let thumbnail: IMediaObject = null;
+    if (content?.info?.thumbnail_url) {
+        thumbnail = {
+            mxc: content.info.thumbnail_url,
+            file: content.info.thumbnail_file,
+        };
+    } else if (content?.info?.thumbnail_file?.url) {
+        thumbnail = {
+            mxc: content.info.thumbnail_file.url,
+            file: content.info.thumbnail_file,
+        };
+    }
+
+    if (content?.url) {
+        return {
+            thumbnail,
+            mxc: content.url,
+            file: content.file,
+        };
+    } else if (content?.file?.url) {
+        return {
+            thumbnail,
+            mxc: content.file.url,
+            file: content.file,
+        };
+    }
+
+    throw new Error("Invalid file provided: cannot determine MXC URI. Has it been redacted?");
+}
diff --git a/src/utils/DecryptFile.js b/src/utils/DecryptFile.js
index d3625d614a..fb3600cd79 100644
--- a/src/utils/DecryptFile.js
+++ b/src/utils/DecryptFile.js
@@ -19,6 +19,7 @@ limitations under the License.
 import encrypt from 'browser-encrypt-attachment';
 // Grab the client so that we can turn mxc:// URLs into https:// URLS.
 import {MatrixClientPeg} from '../MatrixClientPeg';
+import {mediaFromContent} from "../customisations/Media";
 
 // WARNING: We have to be very careful about what mime-types we allow into blobs,
 // as for performance reasons these are now rendered via URL.createObjectURL()
@@ -87,9 +88,9 @@ const ALLOWED_BLOB_MIMETYPES = {
  * @returns {Promise}
  */
 export function decryptFile(file) {
-    const url = MatrixClientPeg.get().mxcUrlToHttp(file.url);
+    const media = mediaFromContent({file});
     // Download the encrypted file as an array buffer.
-    return Promise.resolve(fetch(url)).then(function(response) {
+    return media.downloadSource().then(function(response) {
         return response.arrayBuffer();
     }).then(function(responseData) {
         // Decrypt the array buffer using the information taken from