Have you ever wondered how many Londonian airports have been built since the 1900s? Here is one of the best videos I have seen about this topic. It is one of a series produced by the comedian Jay Foreman. Thanks to this great source of information, you can have the answer as well as some fun.
Another interesting video tells us the train options to connect the six London airports to the City of London:
As you can see, it may cost an arm and a leg to travel to London. However, London airport system is the busiest one in the world. It demands a lot of concentration from its air traffic controllers as shown in this previous post: http://airforces.fr/2016/06/25/london-air-traffic-well-explained/