North London almost entires consists of boroughs on either side of the River Lea which flows south from middle Hertfordshire into the Thames at Leamouth near the north end of Blackwall tunnel.

This part of London is home to dozens of groups of peoples of non-British ethnicity.

The Lea Valley is also where London gets most of its water supply from huge reservoirs between Tottenham and Walthemstow.

The first northern suburb developed in the Soke of Cripplegate in the early twelfth century, but London's growth beyond its Roman northern gates was slower than in other directions, partly because of the marshy ground north of the wall and also because the roads through those gates were less well connected than elsewhere. The parishes that would become north London were almost entirely rural until the Victorian period. Many of these parishes were grouped into an area called the Finsbury division.

In the early 19th century, the arrival of the Regent's Canal in Islington and St Pancras stimulated London's northerly expansion, continuing when the development of the railway network accelerated urbanisation, promoting economic growth in the capital and allowing for the establishment of commuter suburbs.

This trend continued in the twentieth century and was reinforced by motorcar-based commuting until the establishment of the Metropolitan Green Belt, shortly after the Second World War, prevented London from expanding any further. Nowadays, the northern limit is the M25 circumferal motorway.