The home-made device partially exploded at Parsons Green station on September 15, injuring 30 people, but prosecutors say it could have been far worse
The London Underground, or the Tube, is a British transit system which serves a large part of Greater London and some parts of Buckinghamshire, Hertfordshire and Essex. Built in 1863, it is the world's oldest underground railway network and serves 275 stations along 402 kilometres (250 miles) of track. It is the second largest metro system in the world in terms of route miles, after the Shanghai Metro, and is the third busiest in terms of passengers. The first stretch of line - the Metropolitan, or Met - opened on January 10, 1863 and measured six kilometres (nearly four miles), running between Paddington (Bishop's Road) and Farringdon Street. The London Underground carries 1.2 billion passengers per year and is managed and maintained by Transport for London, part of the Greater London Authority.