And in response to Guy Betsy & others:

The whole flight (outbound + return was 4 hours) going was about 2 hours 15 minutes, and return took I estimate 1 hour 45 minutes. When looking at the map, they took a bit of a zig-zag route outbound, but a very straight return route. I understood the reason, which is because CX255 would reach London too early to land (before 6am not allowed to land), so they have to take a longer than needed route while outbound to reach by 6am, for the return, my best guess is that they declared some sort of emergency, which allowed them to fly outside of normal corriders and take a straight route back.

I also thought about landing nearby, but I am pretty certain that they probably wouldn't allow any passengers off the airplane until certain formalities are done, so that means we would probably be stuck onboard for alot further time. I agree 100% with the captains decision to return to HK, but felt that he should have circled and landed much much sooner (within 30 minutes after takeoff he should have made up his decision of turning around.). An hour in the air (round trip) I would understand and could tolerate, but 4 hours was mad.