The LNER Encyclopedia

Here is a British Movietone Newsreel dated September 30, 1935 of A4 Silver Link making a high speed test run from King's Cross with the Silver Jubilee. The title of the newsreel is misleading, saying that the record run was 104 mph. The narrator acknowledges that a top speed of 112 mph was reached. The engine's original American Crosby 3 Chime Whistle is heard twice in this film, once while the engine leaves King's Cross and a second time while the train rushes past the camera at speed later in the film.

https://youtu.be/mDZGpkpDJ4E?t=5s