What do the borough's of Bexley, Bromley, Croydon, Kingston upon Thames and Sutton have in common?

There are 270 London Underground stations serving 5 million people a day, and with 402 km of track the network covers all of London, or does it? Despite the first passenger railway in London (London & Greenwich Railway opening in 1836) being south of the river Thames, it is largely acknowledged that the tube does not serve south London. Walthamstow and Gypsy Hill are roughly the same distance away from central London but in opposite directions, yet Walthamstow is much easier to travel to.

Just 10 percent of all London Underground stations are south of the river Thames. The borough's of Bexley, Bromley, Croydon, Kingston upon Thames and Sutton are all south of the river, and the one thing they have in common is that they have never had a London Underground station. Of 32 London boroughs (and the City of London) it is no surprise that the only five to never have a tube station are in south London.

Lewisham, also south of the river, is another borough that does not have any Underground stations. Until 2007, however, two Underground stations served Lewisham, New Cross and New Cross Gate. These stations were on the East London Line from 1933 (although from 1933 to 1968 the line appeared on the tube map as the same colour as the Metropolitan line), which is now part of the London Overground network.

Hackney, north of the river, is also an interesting borough. Situated in East London, Hackney is often associated with the London Overground, especially with Hackney Downs/Hackney Central being key stations for the network. Despite this association, Hackney does have one London Underground station, Manor House. Served by the Piccadilly line, Manor House station is situated on the border between the boroughs of Hackney and Haringey. The postal address and three of the four entrances are located in the borough of Hackney.

The only other borough that has just one London Underground station is the Royal Borough of Greenwich. The only station in this borough is North Greenwich on the Jubilee line. As far as I am aware, there are 15 stations on the network that are not in a London borough; Amersham, Buckhurst Hill, Chalfont & Latimer, Chesham, Chigwell, Chorleywood, Croxley, Debden, Epping, Loughton, Moor Park, Rickmansworth, Roding Valley, Theydon Bois, and Watford.