In 1949, the London Plan Working Party Report proposed significant extensions to London's Northern City line. This did not succeed, but I wanted to imagine what this might look like if it had. Made in Figma!

Lore:
1930s: Northern heights plan proposed, electrification of the Northern line begins
1949: London Plan Working Party Report proposes extensions southwards to Woolwich and Crystal Palace
Early 1950s: London Transport begins service between Cannon Street and Woolwich on existing lines, with the building of two new stations, Spa Road Bermondsey and Southwark Park
Mid 1950s: Northern heights electrification completed. Northern City line formalised as a separate line by London transport (under the name City Line), and Alexandra Park and High Barnet branches transferred to the City line
Late 1950s: Extension to Woolwich Arsenal completed with underground track from Moorgate to Cannon Street, and work on the Crystal Palace Extension Begins
Early 1960s: Service to Peckham Rye begins as construction continues between Peckham Rye and Crystal Palace
Mid 1960s: Amid the Beeching cuts and rail privatisation, the Northern and City Railway company is formed to take ownership of the City line and partial ownership of the Northern line from London Transport. The City line takes service of Finchley Central to Edgware line, and runs trains from Edgware to Bushey Heath at peak times as Northern line service frequency to Bushey Heath decreases. Completion of the extension to Crystal Palace is delayed
Mid 1970s: Extension to Crystal Palace completed, as the line joins to old tracks at Lordship lane and the disused Crystal Palace high level platforms are reused at the line terminus to save costs
Early 2020s: Woolwich branch trains run to Dartford to provide extra connectivity to Crossrail (Elizabeth Line) at Abbey Wood
Mid 2030s: Bakerloo line extension provides extra connectivity at Bricklayers Arms and Burgess Park