(1956, Jack Hawkins)

London Transport STD14 (DLU324), an all-Leyland Titan TD4 built 1937, on route 13 to London Bridge follows the camera in an atmospheric after dark shot under the opening credits. This could well be stock footage shot much earlier than than the main body of the film, since all STDs had been sold out of service by the end of 1955:

Various AEC RTs are glimpsed in street scenes, including RT3930 (LLU729) on route 159, and an RTW:

….but it's a shame we don't see more of two 'deckers glimpsed in a scene in a scrapyard: