Corrected entry: It's a beautifully staged bit of physical comedy but Otto pulls out his gun, flips it through the air past the airport metal detector and catches it on the other side ... in full view of dozens of customs and immigration officers and civilians in the queue behind him. Even back then the area would have been festooned with CCTV cameras. What, not one person saw someone carrying a large, powerful handgun through airport security?
Corrected entry: In order to tell Archie where the loot is hidden, Ken imitates a flying jet, and Archie immediately states "Heathrow". That may be okay for people who don't know London, but Archie is born and bred - he would have to know that Ken could be alluding to any one of the two major or two large regional airports which serve London - Heathrow, Gatwick, Stansted or Luton (London City wasn't open in those days). He's a lawyer - he wouldn't jump to conclusions like that. (Why didn't he ask Ken to write the address down?!?).