Wiggy:
So many of you guys seem to be totally Pavlovian when to comes to ATC. The buck stops on board, not with ATC. They can invite me to "line up", "take-off" or even "vacate" but I'm not doing any of the above until I'm sure it's safe to do so and I will not get involved in a debate with ATC if I'm handling something critical unless such debate is helpful to me. If that's arrogant so be it. There are umpteen reasons why you may genuinely be unable to either vacate or depart (I have no idea what the case was here)........perhaps the BA pilot should have used the magic word "unable"
Why would it not be safe to vacate?