But what I am saying is that it is a stupid rule that doesn't allow the Commander any discretion in the matter. When people can see the reason for a rule they are much more likely to obey it.
But the Commander is ultimately responsible, otherwise the door would be locked shut from the outside before takeoff and reopened only after landing. And I am sure if there were a truly justified reason for letting pax in there would be no issue. Examples which spring to mind are a medical emergency whereby a doctor/nurse enters the cockpit to relay details of the emergency to ground via radio. Any others?
When I ws a kid (not thaaaat long ago) I would spend plenty of time at the office my Dad worked for, and on weekends I would drive the forklift trucks round the warehouse. Can't imagine that happening with today's h&s. Then again - back then flying anywhere was a luxury I could just dream about, nowadays I fly more often then I drive. Guess it is progress.