(1957, Leo McKern, Michael Redgrave)

An early sequence at London Airport features glimpses of two BEA liveried AEC RF airport buses, and what may be a Bedford SBG:

A sequence in which Paul Daneman drives Michael Redgrave in his open sports car mixes location footage with back projection. The latter features London Transport's Leyland RTL824 (KYY794) on route 96, but there's a bizarre goof when the two are seen reflected in the car's interior mirror: although the two actors are seen correctly reflected, the back projected footage of RTL824 hasn't been reversed!

There are at least two RTLs in this view, maybe as many as five:

In this scene Redgrave leaves a Government office between a Green Line AEC RF and AEC RT3008 (NLE779) on route 12:

(thanks Colin Read)