>>1585416>London’s main train stationsmartass answer: london doesn't have a single main 'London Central' train station, thanks to victorian railway companies building e.g. Fred's Railway to the west, Bill's Railway to the north, and Harry's railway to the south, which is why nowadays there are three great big railway stations all within walking distance (and more further afield), one of which is now international.
ordinary answer: this could be either St Pancras, at ~34.6 million entries/exits (for international passengers and commuters from dormitory towns in Kent & the Midlands); or Waterloo, at ~94.3 million entries/exits (domestic only, western & southwestern passengers). meanwhile the busiest airport in the UK is of course Heathrow, which handles just over 80 million passengers annually, plus roughly 1.5 million tonnes of freight (which railway stations don't carry).
tldr london's busiest train station (Waterloo) carries 10 million more passengers than london's busiest airport (Heathrow), albeit the latter is responsible for freight as well as people
