Karl, you are a rather lucky man, and you obviously haven't visited LHR on a bad day.
On a Sunday afternoon two years ago I sat on the taxiway at LHR for 80 minutes. The BA 757 driver was generous enough to shut down the engines for two times 20 minutes. Other planes in the row must have done the same because the smell of burned kerosene was bearable most of the time.
And yes, a Concorde was waiting for the same time in another row on another taxiway.
I have often said that we don't need supersonic planes. Maybe soon we will need to have only supersonic planes, not to be able to travel faster, but to catch up on the delays.
I hate large hubs, but this time I had to attend a Saturday afternoon wedding in Teddington which is within walking distance from LHR, so there wasn't much choise. And I couldn't care less since it was a Sunday and I had nothing else to do. And I was on a non-stop flight to my destination - no connections needed.
best regards, Preben Norholm
Always keep your number of landings equal to your number of take-offs