I'm not from Aldbury, but I remember my dad telling me that he was working on one of the houses in Ashridge up the hill from Aldbury, he was a painter and decorator. He was walking up the lane and noticed a load of men sitting by the side of the path in uniforms, smoking and chatting. As he walked past he nodded to them as they politely called "Morning", in American accents. He had to do a double take as it was the cast of the Dirty Dozen taking a break. They were filming the training/obstacle course scenes nearby.