Whilst, to the best of my knowledge I have never seen the film, I can claim to have seen it being made!
In 1957 (ish) I used to walk from my home in Hackney to some area of London on a Sunday morning with a friend.
One one visit we finished up at Tower Bridge. We took some steps down the side of the road over the bridge and were confronted by a film crew.
They were filming a scene with an old "coffee shop" on wheels. We stood and watched for some time and the only thing I can remember happening was the boy sneaking up to the counter and stealing a bun. I still remember the coffee shop attendant's face (he was a quite well known supporting actor at the time), but I can't remember his name.
Whether this episode made me decide I wanted to be a Director, I don't know, but 30 years later, I did.