Well, I was on this flight, nothing out of the ordinary until we were above turkey, where there were some strong turbulence. No communication from the cockpit or crew at 1am, but did notice the flight map getting turned off and the arrival time being significantly earlier which I thought was weird. First communication was an hour before landing when we were above the netherlands/germany, captain said due to a mechanical issue, they did not have enough fuel to continue on to HK due to increased fuel burn and if continued would have to divert to an airport in china. So they decided to go back to LHR.