The southern part of the London Borough of Lewisham as well as a small part of the Royal Borough of Greenwich fall outside its boundaries whilst 44 of its 119 districts are in Outer London and its irregular shape stretches to the Greater London boundary at Mill Hill and Scratch Wood and beyond it at Sewardstone.
The storage reservoir is bordered by Sewardstone and Chingford to the east and Brimsdown and Ponders End to the west, and covers 420 acres (170 hectares), making it the largest in London.
Communities outside the administrative area of Greater London that are within the code are Buckhurst Hill, Chigwell, Loughton and Sewardstone in Essex; Borehamwood, Bushey, Carpenders Park, Elstree and South Oxhey in Hertfordshire; and Ewell, Molesey, Thames Ditton and Whyteleafe in Surrey.
The most famous branch of the Sotheby family moved to Bishop Wilton and then to Hackney, London, and Sewardstone in Essex.