A chance remark in Buses Illustrated magazine, October 1967, refers to a Leyland Titan TD1 appearing in a movie about the life of Gertrude Lawrence. Without seeing this scene in the movie I'm now confident this is DR4902, a TD1/Leyland new as National 2849 in 1929. The bus in the movie was actually in Eastern Counties livery, but had 'General' fleetnames and an 11E indicator blind
fitted for filming. Chris Hough adds the film "featured Gertrude Lawrence played by Julie Andrews. Noel Coward was played by his godson Daniel Massey."
Richard Haughey explains, "The Leyland TD1 DR4902 did in fact carry Eastern Counties livery. The bus used to be a Chivers and Sons (Histon) Ltd staff bus and when it was withdrawn by Chivers, the vehicle was given a full overhaul and repaint by Eastern Counties in Cambridge. Chivers then donated the bus to the British Transport Museum. So that is why it was in ECOC livery."
An even earlier vehicle with a starring role is London General K424 (XC8059), a 1920 LGOC-bodied AEC K, seen from every conceivable angle in a lengthy sequence: