This problem was not AI's fault, and it appears they did reasonably well given the circumstances.
As a well travelled aviation person I think that you're being far too generous and I beg to differ with you on this one ExXB. You just DON'T keep pax on board on the ground for 9 hours, and especially when they are at their destination (i.e. London), be it LGW iso LHR. I would say that it came down to some very poor organisation and decision making by the responsible Air India staff and there is absolutely no excuse for it.