The Metropolitan line, colloquially known as the Met, is a London Underground line between Aldgate in the City of London and Amersham and Chesham in Buckinghamshire, with branches to Watford in Hertfordshire and Uxbridge in Hillingdon. Printed in magenta on the tube map, the line is 41.4 miles (66.7 km) in length and serves 34 stations (9 of which are step free). Between Aldgate and Finchley Road, the track is mostly in shallow "cut and cover" tunnels, apart from short sections at Barbican and Farringdon stations. The rest of the line is above ground. 

The line is served by a depot at Neasden. The Metropolitan Railway opened a carriage works at Neasden in 1882 and the following year the locomotive works were moved from Edgware Road. In 1904–05, the depot was refitted to take the new electric multiple units and accommodation enlarged in 1932–3. After the amalgamation into the LTPB, the depot was rebuilt from 1936 to 1939. The depot was upgraded in 2010–11 to enable it to maintain S Stock trains. Trains are also stored overnight at Uxbridge, Watford, Rickmansworth and Wembley Park.