1 Making history - The world’s very first subterranean railway, the Metropolitan line, opened on 9 January 1863. On its first day of operation, 40,000 people reportedly travelled on it.
2 Runaway success - In light of the successful integration of the Metropolitan line, over 250 different proposals for additional Underground lines had been submitted by 1864.
3 Going loco – The first Underground trains were steam locomotives, which burned coke and coal. This fuel led to sulphurous fumes being emitted into the tunnels and stations.
4 Safe and sound – During both World War I and World War II, disused London Underground lines were used as safe storage sites for a number of valuable artefacts from the British Museum.
5 Billion – As of 2013, the London Underground carries over 1 billion passengers per year across 402 kilometres (249 miles) of track, with 270 station stops.