Look, we don't need to justify the security rules to 'aviation fans' with no experience- if other airlines want to go around breaking them into or out of the UK, and the DfT hears about it, then I would imagine their very licence to operate to the UK would be under threat. Let's get this clear- the flight deck is no place to entertain visitors, especially completely inexperienced people who don't know how to conduct themselves. I've been flying 747s with hundreds of people on board, and had visitors with extraordinary behaviour:
*people who were drunk and decided they'd fancy asking to see the FD. It is not nice suddenly realising people are far more inebriated than immediately shows
*'fathers who want to bring their son to see the FD'. Up comes a man with a baby in nappies looking frightened and confused! Men with only children tend to do daft things like that.
*Yappers who can't stop talking, even during the landing
*Enthusiasts who don't know when enough is enough
For the safety of all the people on board, the FD is not the place to make intros and chat away. We had several visitors on a 747 when and engine surged quietly. We were all turning around talking. After a few seconds I had a niggling thought- that 'knock' I heard a few seconds ago sounded just like a surge, but quieter. When I looked to the front and checked the engine instruments, the exhaust temperature of one of the engines was running away uncontrolled. It was an immediate shut down, full power on remaining and start a descent and return. Whilst herding everybody out.
Once again, those days are gone. Good. And as an experienced professional with 38 years as an airline pilot and 21,000 hours, I am not going to get taken to task by an 'enthusiast' in this professional forum who doesn't appear to agree with the regulations as stated by the authorities!