The camera used by Samuel is clearly a rangefinder design which has a separate "viewfinder" to the side of the main lens for framing and rough focusing but the viewfinder shots show a "through the lens" shots as if the camera being used were a single lens reflex (SLR) camera (which uses a mirror and a prism to allow framing and focusing directly through the main lens.) We even see the image in the "viewfinder" being zoomed as if by the main lens, when what Samuel would see using a rangefinder camera would be a fixed focal length image regardless of the actual focal length of the main lens.
The creepy people posing as MI5 have fake American accents.