The line was completed and opened in January 1930, although the planned extension of the DR was not implemented and the service was provided by the Southern Railway.

The bill proposed a 5.5-mile (8.9 km) line with ten stations, to be operated by electric trains, which would provide a service taking 32 minutes to reach Waterloo from Sutton.

The LB&SCR opposed the line on the grounds that it would compete with its own services from Sutton to Central London, and claimed that its own planned electrification of its lines to Victoria and London Bridge would offer quicker journeys than the W&SR route.

[7] Intermediate stations were approved for Elm Grove in Wimbledon, adjacent to the All England Lawn Tennis and Croquet Club's original grounds, Cannon Hill, Merton Park, Morden, Elm Farm, Sutton Common, Collingwood Road and Cheam.

The requested extension of time and other powers were granted by the Wimbledon and Sutton Railway Act 1913 (3 & 4 Geo.

[11] In late 1913, changes were made to the track layout at Wimbledon station, including a new platform for use by the W&SR line trains, and land for the junctions with the L&SWR mainline was purchased.

[11] On 16 November 1914, after the outbreak of war, the DR gave notice of another bill which sought a further extension of time for land purchases.

[18] War-time restrictions prevented any construction and so extensions to the earlier acts were granted each year from 1918 to 1922 to give a final date of 26 July 1924 for completion of the compulsory purchase.

[23] The UERL rejected Walker's plan, claiming that the entire extension to Morden was needed as that was the only place to build the necessary depot.

The C&SLR soon started construction of its southern extension which opened to a terminus at Morden on 13 September 1926,[28] with a depot south of the station and within 200 yards (183 m) of the W&SR route, although no connection was made between the two lines.

Without the extension of the District line to Sutton, the additional tracks between Wimbledon and Putney were not required and the work was not carried out.

[11] Once the C&SLR line was opened, the Underground company established a network of bus routes to the south, using Morden station as their hub.

Designed for operation exclusively by the electric multiple unit, extensive embankments and cuttings were constructed and steep gradients up to 1 in 44 (2.27%) and tight-radius curves were employed.

Only 35 chains (0.438 mi or 0.705 km) of the route was built as level track and 24 bridges were required, the largest of which spans 120 feet (37 m) over the A24 close to Morden Park.

[31] Work from Wimbledon to South Merton was completed quickly, so that services could begin running as a single-track operation on 7 July 1929.

[30] The remainder of the line opened on 5 January 1930,[30] more than forty-five years after the first Wimbledon to Sutton link was proposed.

[32] Ordinary ticket sales from Morden South station increased from 9,840 in 1930 to 50,817 in 1938 but, from the SR's perspective, the line was not a great success.

The service, originally operating from West Croydon to Holborn Viaduct station in Central London, was slow and indirect and many of the potential passengers from the line's catchment area continued to use the buses and tube route via Morden.