Some years ago I was operating a scheduled service from one of the more pleasant West African countries and was informed that the President of that country was travelling to London on our flight.
We waited 45 minutes for him to emerge from the VIP lounge. I would dearly have loved to depart on time and without him but the poilitical consequences of doing so, assuming ATC would have let us go anyway, did not bear thinking about.
It is interesting that any member of royalty in the UK would never dream of keeping a flight waiting. I suppose it all comes down to manners and courtesy and a certain cultural difference where those that live high of the hog in Africa treat those they consider beneath them with utter contempt.