First incarnation of this thriller series:
Season 1 Episode 20: Name Date and Place
John Drake (Patrick McGoohan) boards London Transport RTW242 (KLB972) on route 74 to Earls Court:
The following scene on the upper deck has trolleybus wires visible through the rear window.
As Drake alights, apparently in Acton Vale in West London, two trolleybuses pass eachother.
This is one of them: