The flight back can be miserable at this time of year. I just got back from Harry Honkers on BA; from sundown in Shenzhen at 6pm local to dawn in London at around 7:30am local (the flight got in at just past 5am) was getting on for a 21 hour night.
Mind you, it was enlivened by Nigel. We were about an hour late taking off due to two pax not boarding and their baggage getting deplaned, which occasioned a PA from Nige saying "Terribly sorry for this delay. If I had my way, passengers who did this would be lined up against a wall and shot" (much laughter over the PA, short pause in proceedings).
We made up the time: just after we'd done the usual LHR taxithon and got to the stand, another PA from the pointy bit said "And if you look out of the left-hand side of the aircraft you can see that the other BA flight which took off a minute after us from Hong Kong is just landing now. He had a bad hair night, let me tell you."