Film and TV crews often film very early in the morning during the summer when in towns and cities. This keeps traffic to a minimum and you don't have to cope with memblics wandering around. You might notice long shadows as a giveaway, I haven't seen this film in a long time, so I don't know if they are obvious.
If you look at the old Monty Python film sketches there is no traffic on those, I would guess they are filmed very early as well. The odd thing, though, is there are no cars parked on every available inch of kerb. It looks quite odd because London doesn't look like that today. (Mind you we were too poor to 'ave cars in the Seventies.)
And cue the Four Yorkshiremen again.
Biting the hand that feeds IT
