A couple of years ago I was flying back to HKG from LHR on BA27. We had an engine surge on t/o and after a couple of hours enroute, the decision was made to go back to LHR. By the time we arrived back in the UK it was about 2am and we were all put up in a hotel overnight and told that we would be rescheduled for the next afternoon. So the following day, we flew out to HKG on flight BA27Y, a few hours ahead of that day's BA27.