South Western Railway services between the capital and Reading use the line west of Wokingham and the same company operates between Guildford and Ash en route to Aldershot.

[1][3] The 2015 "Surrey Rail Strategy" noted that 56% of passengers on the route connect to services on other railway lines and that a quarter of journeys either start or end at Reading.

[72] The company's stated objective was to build a line linking the three towns in its name to "secure through traffic passing between the West, North and Midlands and the Channel Ports avoiding the congestion of London and thus saving time, distance and expense.

By mid-January, the RG&RR had bought out the rival Reading and Reigate Company, promoted by David Mocatta, which had proposed a line with similar aims.

In the same month, the South Eastern Railway (SER), which had wanted to build its own short branch from Reigate Junction to Dorking, offered to operate the line.

[75] The act gave the RG&RR the powers to construct the section of the line from Dorking to Gomshall, if it was not built in time by the London & Portsmouth Direct Atmospheric Railway Company.

In mid-1848, the plans for the London & Portsmouth Direct Atmospheric Railway were abandoned[78] and the contract to build the Dorking-Shalford Junction section of the RG&RR was awarded to Charles Henfrey that May.

He disagreed strongly with Stephenson's alterations to the station arrangement at Reading but was unable to persuade the RG&RR board to reinstate Giles's original scheme.

He also suggested building the Dorking to Farnborough section as single track, but the board decided to continue with Giles's plans for a fully double-tracked railway.

[34] Following the conclusion of negotiations with the LSWR, a bill authorising the curve linking the RG&RR to the South West Main Line at Farnborough was granted royal assent on 26 June 1849.

The collapse of St Catherine's Tunnel delayed the completion of the LSWR-constructed Shalford Junction to Guildford section, which finally opened on 15 October 1849.

[80][87][j] The initial daily full-line timetable included six trains from London to Reading, with five in the opposite direction, supplemented with an early morning departure from Guildford to the capital and an equivalent mid-evening return.

[90] Through trains from the GWR at Reading were introduced on 1 July 1863 with a daily Birkenhead to Dover return working, but disappointing passenger numbers resulted in the service being withdrawn in October 1868.

[98] The Staines, Wokingham and Woking Junction Railway (SW&WR), which had been granted running powers over the Wokingham-Reading section in 1853, opened its line from Ascot on 9 July 1856.

[96][98] A second link at Reading, which passed under the Great Western Main Line and which was owned by the GWR and SW&WR, was opened to goods services on 1 December 1858 and to passenger trains on 17 January the following year.

[56] The fourth link, a tight curve to the Alton line allowing SER trains from Ash to run into Aldershot station, was completed in 1879.

[101] New embankments and a wooden trestle bridge across the River Wey were constructed by the SER to create a triangular junction at Shalford, providing an alternative route to the capital.

[31] It is unclear whether track was ever laid over the spur, but the SER decided not to continue its work, fearing that completion would violate its long-standing agreement with the London, Brighton and South Coast Railway not to compete for traffic to Portsmouth.

[112] On 4 January that year, Class 206 units, nicknamed Tadpoles and officially designated 3R, began operating an hourly stopping service between Tonbridge and Reading, calling at all stations except Winnersh and Earley.

[120][121] As the result of the privatisation of British Rail, the North Downs Line was included in the Thames Trains franchise, won by the Go-Ahead Group in 1996.

[125][126] In the 2010s, additional platforms were opened at Reading,[127] Redhill[128] and Gatwick Airport stations,[129][130] to increase capacity for trains using the North Downs Line and other passenger services.

A major project to renew the signals in the Wokingham area and to transfer control of the northwestern part of the line to the Basingstoke rail operations centre was completed in February 2024.

Brockham Limeworks and Brickworks, to the east of Dorking, was connected to the North Downs Line by a standard-gauge siding but also had a small 2 ft (610 mm) system.

[160][161] The travelling post office train from Dover to Manchester Piccadilly via Tonbridge, Redhill, Guildford and Reading was routed along the line from May 1988[147] until 1996, when a new road and rail postal hub opened at Willesden.

[85] The Network Rail 2008 Strategic Business Plan recommended an enhancement project to enable freight traffic from the Channel Tunnel to use the line.

A study for Surrey County Council, published in two parts in 1995 and 1996, recommended that the Dorking–Reigate section be electrified and a north–east link from the Mole Valley Line be built, to enable a loop service to operate via Epsom, Redhill and East Croydon.

[165] The following year, Surrey County Council suggested that electrification of the full length of the North Downs Line would create around 8,000 jobs and would stimulate £1.9 billion of economic growth, based on research by four local enterprise partnerships.

[166][167] The "North Downs Line Traction Decarbonisation Strategy", published by Network Rail in 2024, evaluated the costs and benefits of completely electrifying the route.

Whilst introducing a third train per hour between Reading and Redhill would allow stops to be removed from Reading–Gatwick services, it would deliver only a marginal improvement in the financial performance of the line.

This option was dismissed in the 1995/6 Surrey County Council reports as it was thought that the stopping train frequencies on the two lines would be too low for suitable connections.