London's sprawling Underground network, with its 272 stations and 402 kilometres of track, is a marvel of urban transport. Yet, it could have been even larger. A significant extension planned in the 1930s promised to add three more stations to the Tube map, a project that was ultimately consigned to history.
The Ambitious Northern Heights Plan
In the 1930s, Transport for London's predecessor devised a major expansion for the Northern line. Known as the 'Northern heights' project, it aimed to extend the Mill Hill East branch northwest beyond its terminus at Edgware.
The plan was remarkably advanced. It proposed new stations at Brockley Hill, Elstree South, and Bushey Heath, with the latter becoming a brand new terminus for the line. This would have created a vital link between the two separate branches of the Northern line, integrating existing railway infrastructure from the Great Northern Railway.
Evidence of a Frozen Project
Physical proof of this grand ambition still exists today. If you look carefully at the end of the platforms at Edgware station, you can see where the tunnel continues, sealed off and leading nowhere. More strikingly, at the intended site of Brockley Hill station, you can find half-constructed brick arches that were meant to support an elevated platform, alongside an abandoned bus stop lay-by.
These remnants show how much work had already begun before the project was halted. Builders had initiated tunnels and infrastructure, making its cancellation a significant decision.
Why the Stations Were Never Built
The catalyst for the project's end was the Second World War. The conflict caused monumental disruption, diverting resources and labour. After the war, the introduction of the Green Belt legislation in 1947 fundamentally changed the landscape—literally and figuratively.
This new law restricted house building in the areas surrounding the planned stations, drastically reducing the projected passenger numbers. With the original purpose undermined, the extension was officially abandoned in 1954. The partly built Brockley Hill station was later mostly demolished, leaving only the viaduct remnants visible now.
Today, the Northern line still ends at Edgware, and these three stations remain as ghostly 'what-ifs' in London's extensive transport history, a permanent reminder of a different future for the city's Underground.
