(1971, Richard Attenborough, John Hurt, Judy Geeson)

“Beryl and Timothy Evans board a London Transport RF displaying route 15 on its rear screen. This is not very authentic; the events in this film occurred in 1949, and an RT would be a more likely vehicle for this route, or perhaps an STL or similar.” (thanks Alan Sinclair)
RF512 (MXX489) was in fact new in 1953: