Can anyone identify the dates of the uniforms? Particularly the large peaked caps with white tops of the gunners? They definitely do not seem 'at war' 1940.
They look like naval personnel in the film in the OP to me. considering they are shooting a QF 2 pdr. on that tracked vehicle, it would have made sense to utilize a RN gun crew already trained in its use.
I'm pretty sure it's a 1 pounder.