Ealing Films' "The Ladykillers" released in colour in 1955 is brimming with period vehicles, including this 2RT2 running along Euston Road outside Kings Cross Station towards the Caledonian Road.

http://www.imcdb.org/movie_48281-The-Ladykillers.html
http://www.imcdb.org/vehicles_make-AEC_model-Regent+III+RT.html