A few years ago I made a Freedom of Information Request to the UK MOD asking whether the Prime Minister, Tony Blair, had ever been invited onto the flight deck of any RAF plane that he had been flying on.
The Prime Minister is commander in chief of the armed forces, i.e. boss of the military. Would he need to be invited or just command entry? He could change whatever SOP's for a few moments to suit.
Was there not a case a few years ago of a UK a/c on a private charter for a football club; one of the players asked to visit the flight deck - damn it they'd paid for the a/c - it was allowed and the captain fired?