The people who suffered jetlag on that service were those who took advantage of a whole UK afternon of drinking, fell asleep around 20:00 hrs UK time, then got woken up for landing about an hour later.... Even if you slept earlier the chances of hitting REM with a pickled liver were never high. These individuals would then go through hell every afternoon at around 15:00 hrs for the next week, and wake for breakfast at 03:00 hrs.

Everyone's response to jetlag is very different, I don't get it at all, which is just as well given my schedule, but I do plan a bit. So in the case of that flight I'd wake up a few hours early for several days beforehand, plan on either 4 or 6 hours sleep (never 5 or 7) on board, definitely no alcohol but plenty of other liquids, get some exercise outdoors on arrival in Hong Kong and target 21:00 hours HK time for bed. So I'd get a whole day out of it. I do different things on different routes/times, but that's what I did for that that one and its current CX alternative.