Dudding Hill line

In 1990 Crossrail plans were announced by Secretary of State of Transport Cecil Parkinson, which would have seen trains using part of the line to reach the Chiltern line to Aylesbury. A new viaduct would have run alongside the Grand Union Canal from Old Oak Common to Harlesden, and the first stop out of Paddington station would have been Wembley Park, for connections to the Metropolitan line and Jubilee line. Later plans replaced all this with a new tunnel connection,[9] and finally the Aylesbury branch was dropped completely from the scheme.[10]

During the late 1990s, BAA planned to run some or possibly all Heathrow Express trains along the line to St. Pancras.[11]

In early 2008, the London Group of the Campaign for Better Transport published a plan for a North and West London Light Railway.[12] The line has been identified by Campaign for a Better Transport as a candidate for reopening.[13]

In July 2008, a high-speed rail network was proposed by the 2M Group, a campaigning group representing people affected by Heathrow Airport expansion, as an alternative to increased air traffic. A rail route running from Heathrow to Cambridge would connect with the Midland Main Line at a "Cricklewood Interchange" station, using new track north from Heathrow to Ruislip, then the Great Central Line (nowadays the Chiltern main line) to Neasden, then a short northernmost section of the Dudding Hill Line from Neasden to Brent Cross.[14]

After several independent efforts, in early 2009 the British Government began an official detailed study of possible high-speed rail routes

In June 2013, the Mayor of London and the London Boroughs of Brent, Ealing and Hammersmith & Fulham released 'vision' consultation documents[15] about the Old Oak Common area of west London. This involves a major development area for London, based around a new Old Oak Common station for High Speed 2 and Great Western Main Line, including Crossrail.

The vision mentions various connections to the Transport for London London Overground system, connecting Old Oak to the North London Line, West London Line, and two new branches, to Hounslow, and via the Dudding Hill Line to Thameslink stations on the Midland Main Line.

In October 2016, a report by Jonathan Manns and Dr Nicholas Falk, on behalf of the UK Government's All Party Parliamentary Group for London's Planning and Built Environment, proposed new orbital rail links in West London modelled on Swift Rail or Rapid Transit, connecting existing communities and those which could accommodate additional growth. It encouraged West London Business (West London Alliance) to reconsider work it had commissioned in 2001 which flagged the scope to connect Old Oak Common and Brent Cross along the Dudding Hill line. This connection was supported in addition to smaller connections using underused or unused existing connections.[16] It was agreed at the following meeting of the West London Economic Prosperity Board, in December 2016, to undertake further analysis on the feasibility of establishing an orbital passenger rail connecting regeneration schemes.[17] The findings were presented in June 2017, on the basis of which the Board voted to progress engagement with the Mayor of London around a West London Orbital.[18] The Mayor put forward a proposal to work with the West London Alliance and others to deliver a West London Orbital in March 2018, following publication by the West London Alliance of a proposal.[19]

In September 2017, the West London Alliance, a partnership between the local authorities of Barnet, Brent, Ealing, Hammersmith and Fulham, Harrow, Hillingdon and Hounslow, proposed a new West London Orbital Railway passenger service that would connect Hounslow with Hendon and West Hampstead via the Dudding Hill line. New stations would be built at Neasden and Harlesden, and an interchange with the Elizabeth Line and the Overground's North London line in the vicinity of Old Oak Common on Victoria Road, North Acton.

On the Midland Main Line new platforms would be built at Hendon and at Cricklewood and West Hampstead, while the Hendon service could also call at the planned new station for Thameslink services at Brent Cross/Staples Corner. The West Hampstead branch would be complete by 2026 and the Hendon branch by 2029 with 4 trains per hour on each branch end.[20] The project's benefit-to-cost ratio is estimated to be in excess of 50:1.[21][22]