Well I know I am being a bit picky here, but I'd never turn up at NCL that early, security if it takes 5 minutes would be deep into Red Button territory. And I'd expect to be on HEX or the tube in under 10 minutes of arrival at T5, the joys of HBO. NCL is well placed for residents locally, in terms of the A1 and the middle class housing locally. So I would shave a good 90 minutes off the flying time, and to be fair, 15 minutes off the train time too.

In my case, I'm aware that the late service from NCL to LHR gets the "benefit" of a whole day of accumulated delays for crew, aircraft and LHR airport. So I neatly avoid the problem nine times out of ten.

I live 45 minutes from the airport - much further away than most users. So if the service is on time I leave home at 18:45, to arrive 19:30, depart 20:10. However before setting off I would check whether BA1336 has left London, it's scheduled to do so at 18:25. Yesteday it actually left the gate at T5 at 19:08, and took off at 19:32. So in that situation I would simply not leave until the aircraft has taken off, say 19:40, and I would be at the NCL lounge 5 or 10 minutes before boarding.