For about twelve years, the railway ran alongside the Kensington Canal, formerly Counter's Creek, a minor tributary of the Thames River until it was filled in, the water course turned into a sewer and the future District line built over it.

Renamed the West London Railway (WLR) the line officially opened on 27 May 1844, and regular services began on 10 June, but before that trials to demonstrate the potential of the atmospheric railway system had been held from 1840 to 1843 on a half-mile section of track adjacent to Wormwood Scrubs, leased to that system's promoters;[2] The WLR used conventional power but was not a commercial success.

An Act of 1845 authorised the GWR and the L&BR (which became part of the London and North Western Railway [LNWR] in 1846) to take a joint lease of the WLR.

For a time, the West London line formed part of the GWR's Middle Circle route (1872–1905) which ran (clockwise) from Mansion House to Aldgate (originally Moorgate) via Earl's Court, Kensington Olympia, Latimer Road and Baker Street.

Competition from the new deep-level Underground railways and electric tramways took away custom by offering more direct routes into Central London.

For many years, limited passenger trains ran on workday mornings and evenings, to carry workers at the Post Office Savings Bank headquarters, Blythe House, near Olympia from Clapham Junction and back again, but these services were not publicly advertised.

Kensington Olympia was used as late as the 1970s as a location for collecting milk tanks (for the west country) from various terminals in the London area such as Ilford.

Channel Tunnel infrastructure work in 1993 electrified the line at 750 V DC third rail from the South to the North Pole depot.

New stations opened at Shepherd's Bush in 2008 and Imperial Wharf in 2009, bringing main line rail services to a large catchment area in West London.

[14] Intercity prior to 1997, and then from 1997 to 2007 Virgin CrossCountry operated a long-distance service between Edinburgh Waverley and Manchester Piccadilly and Brighton, in addition Intercity operated Summer Saturday services Liverpool to Dover Western Docks and Manchester to Eastbourne which use the West London line route to cross from Acton Main Line, stopping at Olympia and passing through Clapham Junction.

[17] For a brief period, Southern and Connex also operated a direct service from Rugby to Brighton via Gatwick Airport, but this was withdrawn in 2001.

The service was curtailed due to the difficulty in securing train paths in the congested West Midlands, and operated only as far as Rugby.

With engineering works on the upgrade of the West Coast Main Line, the service was shortened to terminate at Watford, and was discontinued, later revived as a shorter regional route as part of the South Central franchise in 2008.

Due to congestion on the West Coast Main Line, the service did not run north of Milton Keynes Central,[22] and in May 2022 was curtailed to Watford Junction.

A 2010 Department for Transport command paper highlights opportunities for interchanges at Old Oak Common with London Underground, London Overground and Southern's cross-London services,[26] while a report prepared by Terry Farrell and Partners for the Borough of Hammersmith & Fulham proposes the construction of an overhead light rail, automated people mover or personal rapid transit system linking "Old Oak Central" [sic] with Willesden Junction.

The proposal envisages diverting the NLL Richmond route to curve around the eastern side of Old Oak Common, and re-routing the WLL to branch west south of the Mitre Bridge before curving north along a short section of the Dudding Hill Line to join the West Coast Main Line.

The NLL and WLL would meet at a point on the southern side of Old Oak Common, adjacent to Wormwood Scrubs, where new interchange platforms would be built.

Alternative versions of this scheme also consider cheaper options such as terminating the WLL at Old Oak Common or two separate London Overground stations.