it carried many trains to the northwest, and it was heavily used in the 1960s when electrification work restricted capacity on the West Coast Main Line (WCML); but when that project was completed,[when?]

All local trains on the route were diverted to Marylebone via Sudbury in 1963, and Greenford station on the New North Main Line was closed.

In the early 1990s the New North route was reduced to a single-track layout between Old Oak Common and Park Royal and between Greenford and South Ruislip.

Until December 2018 it was used for goods trains carrying refuse from London and was a diversionary route when the normal lines to Marylebone or Paddington were closed.

For operational reasons such as balancing wheel wear, trains including those of Heathrow Express which were affected by tight track at Heathrow Junction have been turned using the London end of the NNML, its triangular junction with the Greenford Branch Line and the GWML through Ealing.

At weekends between 2008 and 2011 when major engineering works were taking place on the West Coast Main Line, it was also used by Virgin Trains' London Euston to Birmingham International Blockade Buster service, which ran via Willesden, Acton Main Line, Ealing Broadway, Greenford, High Wycombe, Banbury and Coventry using Super Voyager sets up to 15 carriages long.

[7] A siding was built in 1980 to serve the then-new waste transfer station at Victoria Road, South Ruislip.

[8] Old Oak Common station is proposed for the combined part of the route with the GWML, for connections to and from the Elizabeth line.

Additional tunnelling under the New North Main Line will keep the line free for other potential passenger services, as in the April 2013 published decision by High Speed 2 and the Department for Transport to recommend further bore tunnelling under the 5.6 miles (9.0 km) of the 'Northolt Corridor' within the London Borough of Ealing.

Cost neutrality flows from avoiding 20 bridge replacements, particularly 3+1⁄2 years to replace road over rail bridges at the Hanger Lane Gyratory System, amenity disruption, the construction of intermediate tunnel portals and the likelihood of substantial compensation payments.

[11] A think tank with lobby group support has suggested that the line be used as part of services linking High Speed 1 to Heathrow Airport.

Until recently the entrance to a passenger stairwell was visible on the London-bound side of the Network Rail tracks.

These served several local businesses and were also used to store spare British Rail and London Underground stock on occasion.

It was closed in 1948 following the extension of the Central line to West Ruislip, the current tube station opening on 21 November 1948.

[16] This siding served the British Bath Company factory[17] beside the Paddington Branch of the Grand Union Canal.

[16] The present station, adjacent to the original, was built as part of the Central line extension of the 1935–40 New Works Programme of the London Passenger Transport Board.

These originally served the local Royal Mail distribution centre and sorting office, but were disused for this purpose for decades until eventual closure in the early 2000s.

It had long wooden platforms and pagoda shelters, on an embankment reached by sloping paths west of Horsenden Lane South.

[19] Twyford Abbey Halt, located just to the east of the current Hanger Lane tube station, was opened by the GWR on 1 May 1904.

[28] The NNML platforms closed when the Central line was extended on new track from North Acton to Greenford station in 1947.

From May 2008 only freight trains and a token once-daily passenger service provided by Chiltern Railways used this stretch of line until closure in December 2018.

It closed in 1947 without a replacement when the Central line of London Underground was extended from North Acton to West Ruislip alongside the NNML under the 1935–1940 New Works Programme delayed by World War II.