It was anticipated the line would be operational by the mid-2020s because it makes use of existing underused rail infrastructure rather than requiring significant lengths of new track or tunnels to be built.

It has no stations, no electrification and a 30 mph (48 km/h) speed limit with semaphore signalling, and is lightly used by freight and very occasional passenger charter trains.

In March 2017 the West London Alliance group of local authorities commissioned a study to assess the feasibility of the line so that a decision could be taken as to whether it merited pursuing further.

[4] In March 2018 the Mayor's Transport Strategy was published, which includes a proposal for this orbital connection to Old Oak between Hounslow and Brent Cross.

[13] In March 2023, Mayor Sadiq Khan said that plans were progressing for the link and that timetable assessment by Network Rail was nearly complete.

[14][15] A number of routes have previously been examined for new orbital tube lines and improved connectivity across West and North London.

It was considered that the most likely route of the previous proposal would be a north–south route running from Brent Cross to Surbiton, via Wembley Park, Ealing Broadway, Richmond and Kingston fully underground, connecting several London Underground and National Rail lines, including the Elizabeth line at Ealing Broadway.