The London Underground
The London Underground, without it the city would struggle to survive.
The London Underground is a transit system that serves much of Greater London and some neighbouring areas. It is the world's oldest underground system, and is one of the longest in terms of route length. Services began on 10th January 1863 on the Metropolitan Railway most of the initial route is now part of the Hammersmith and City line Despite its name, about 55% of the network is above ground. Popular local names include the Underground, more colloquially the Tube, in reference to the cylindrical shape of the system's deep-bore tunnels.
The Underground serves 275 stations and twelve lines and runs over 408 km (253 miles) of line. There are also numerous closed stations In 2005–2006, 971 million passengers used the Underground and for the first time ever in 2006–2007, over one billion passengers were recorded. As of March 2007, just over 3 million passengers use the Underground each day, with an average of 3.4 million passengers on weekdays.
This is the official website of the Transport for London, on this site you can find out if there are engineering works (which happen a lot at weekends) and also a journey planner. One bit of advice is an Oyster card this site explains everything about them, but they are a very cheap way of travelling around on the Underground and buses.
Any question's email John