Crossrail 2

Crossrail 2 is a proposed rail route in South East England, running between Surrey and Hertfordshire providing a new rail link across London on the Crossrail network. It would connect the South Western Main Line to the West Anglia Main Line, via Victoria and Kings Cross St. Pancras, intended to alleviate severe overcrowding that would otherwise occur on commuter rail routes into Central London by the 2030s.[1][2] The project was earlier known as the Chelsea–Hackney line (or Chelney line) in reference to a potential route. The plan for a line on this alignment has existed in various forms since 1970.

More information on the Wikipedia page.