I was caught out one day trying to get into the heliroutes one day. Checked notams and indeed there was a royal helicopter flight taking place. I took off, saw the royal flight and avoided it. But when I tried to get into the London zone, clearance was denied owing to priority traffic. This I though was little strange I had just flown around a member of the Royal Family using the Rainbow callsign (senior member of the family I think)
It all became clear when an american accent came on the radio claiming to be Marine 01. Six helicopters one of which had Bill Clinton onboard. He wasn't even the president (Geo W. had just taken over). Sick. Why do the Americans come over here and just ignore our system? So we followed them for a while. That annoyed them!