The first Pan Am '747 to arrive at Heathrow did a demo flight for VIPs and local dignitaries in the afternoon just out to Brecon and back.
I was the radar monitor on the frequency on which it contacted London Control after departure (I supplied information to the radar controller by writing flight details on a perspex board with a TV camera behind it which the radar controller then referred to) and remember his immortal first words when he called up:
'London Clipper XXX; we're not gonna make four thousand (feet) by Woodley'.
(Remember it only had about 200 people on board and was not fully fuelled for a transatlantic flight)