(London Weekend sitcom 1969-70)

Episode 1.04: Peace and Quiet
Central character Michael Upton (Barry Evans) steps off a bus. It's much filmed London Transport RTL1557 (OLD666):

Later he gets back on the bus and waits for it to start off.

When nothing happens he goes to the front of the bus he finds it's having a wheel changed. It's RTL1557 again, but in this case it's carrying a very odd fleet number - RTE557: