My original query was about the legality of keeping people on board against their will when they had arrived at a point where the plane was declared to have landed. I still think this was false imprisonment, and the Police, instead of keeping the passengers calm, should have been helping them exercise their rights. Ironically, if anyone had been arrested and taken into custody, the Police would have been obliged to offer them food and drink at regular intervals, which is more than they were getting on the plane.
As far as Air India management is concerned, this situation has to be their responsibility and they should have plans for this. Even if they do not have a service base at Gatwick, they should have a "what if one of our planes loaded with passengers has to divert to Gatwick?" scenario in their contingency planning as part of running a responsible airline. At the very least, organising drinks and a hot meal once the delay was known to be significant, even allowing for the incremental nature of the delay, should have been a priority. If the plane was then given clearance to leave Gatwick before the passengers could have their meal, it would have been money well spent as insurance against poor
PR - at what? £10 per passenger at most. If solving this problem was above the pay grade of the Air India duty manager, why wasn't someone more senior involved? I am sorry, but as a regular passenger I don't buy the "it was not their fault" argument at all.