If New York is the city that never sleeps, London is the city that prefers to get a full night’s rest, thank you very much. Much as London is a cosmopolitan place, it can also be amusingly old-fashioned about bedtime: restaurants tend to stop serving food at 10pm, pubs and bars can close as early as 11pm, and while recent efforts towards making the Night Tube a thing are sort of working, public transit options are definitely less robust in the wee hours.
However, while it’s something of a rite of passage for Londoners—perhaps after one too many pints—to fall asleep on the night bus (the main nocturnal mode of transport), if you think you’re at risk of that, save time and order a taxi instead.