London Underground ticketing destinations and most interchange stations are in zone 1, meaning that most journeys over similar distances will cost the same. A few stations in the north east of the network, on the Central line, outside Greater London (in the Epping Forest district) are in zones 4, 5 and 6. In the north west of the network, on the Metropolitan line, zones 7, 8 and 9 (formerly A - D) cover stations outside Greater London including Amersham and Chesham in the Chiltern district of Buckinghamshire. Unlike the lower numbered zones, these ancillary areas do not encircle the capital. Some stations are
M25 motorway this time depicting these short sections named the route as the M16 but this changed before completion. The section from Potters Bar to the Dartford Tunnel was constructed between 1979 and 1982. Construction of the M25 continued in stages until its completion in 1986. Prime Minister Margaret Thatcher officially opened the M25 on 29 October 1986, with a ceremony in the section between J22 and J23 (London Colney and South Mimms). The initial tenders for the construction of the M25 totalled £631.9 million. This did not include compulsory purchase of land and subsequent upgrades and repairs. Soon after the motorway