Blind Date AKA Chance Meeting
(1959, Stanley Baker, Hardy Kruger)
Opens with Kruger's character alighting from London Transport Leyland RTL847 (KYY 819):
It's followed by another, RTL732 (KXW82):
Odd passing RT family buses:
Jon Price also notes “Some shots at Heathrow Airport show background shots of BEA RF coaches and an airside articulated tractor/trailer style bus.”
(the name on the side is 'London Airport')
…and Kruger's character exits aboard RTL829 (KYY799), with other RT family buses in background: