One of my favourite bits of the film is where the plane (Me 108 IIRC?) flies along just above the beach whilst the invasion is going on.
Remember, this was in the days before CGI, so all those tanks (including a CHURCHILL carpet layer I recall) and blokes were really there.
I always have a little chuckle at the bit where the German sentry scans the sea where there is nothing. A moment later, he looks back to see the invasion fleet. My grandad loved that bit for some reason.