Until about a year ago I was in London, using TFL to get around was always a bit of a nightmare. On top of the rush hour craziness, every weekend there would be planned disruptions, every day there would be non-planned disruptions. And every day the announcements in the tube would end with the usual signature: all other lines are operating a normal service
During the London Olympic games I received a new email from TFL every day informing me that the tube is going to be too busy to support all of its usual customers and those generated by the sporting event. In short, the emails advised me to avoid going to the places I usually go to, especially at the times I usually do so. The best thing to do, according to TFL, was to go where nobody every goes using the last or the first trains.
In the end TFL thanked their clients for changing the way they travelled to help those with tickets get to their events. I heard from a good source that London was quite empty during the games, many either worked from home or just left town I guess.