Any 1950s war film with Richard Attenborough (and/or John Mills) is a classic as far as I'm concerned. But my favourite is one that was actually made during WW2 in 1943- In Which We Serve. A blatant propaganda/morale boosting type film loosely based on the exploits of Louis Mountbatten when he was Captain of HMS Kelly. It also starred the brilliant Noel Coward in the captain's role. Richard Attenborough's role, although playing a minor part as a sailor who deserts his post during a battle, is an enduring part of the film due to his sheer acting ability and presence. And there's a scene filmed on Plymouth Hoe.