Will say, for all the complaining about BA (including my own), I was recently stuck on the tarmac at LHR for just under 3 hours and the FAs were literally begging us to drink water that they passed out. It was a fairly warm day, but not particularly hot in the cabin because the pilot left an engine running for AC. I would not have wanted to unload and than reload a 747, and they did a reasonably good job of keeping us apprised. Probably in part because at least half the passengers aboard could see the fuel pouring out of the wing tank onto the tarmac. Overall they did a pretty good job, short of passing out legroom, which is what we really needed for a three hours delayed transatlantic flight.