(1966, Alberto Sordi)

An Italian antiques dealer dreams of coming to London and being part of 'Swinging London' - so he does. He's a likeable character, and he has various adventures.
A scene at London Airport features BEA AEC Regal IVs in two different liveries:

Perugia trolleybus 102, a 1949 Breda 2GU, passes the window of his shop back home.

As our hero buys a copy of the Times newspaper, a Bristol MW/Eastern Coachworks passes behind (UnitedCounties? Eastern National?), and inevitably several London Transport AEC Routemasters:

He tries to catch a bus, by raising his umbrella, but the handle catches on the handrail, and he's left running behind the bus holding on to his umbrella. When the bus draws up at the next stop, the conductress sells him a ticket for his journey. The bus in question is an RT, in London Transport red, but by the time this was filmed, it had been sold to Margo of Streatham, hence the fleetname. It's RT3907 (LLU706):