[2] From the W&SR's inception, the District Railway (DR) was a shareholder of the company and had rights to run trains over the line when it was built.

In the 1920s, the Underground Electric Railways Company of London (UERL, precursor of London Underground) planned, through its ownership of the DR and the City and South London Railway (C&SLR, now the Northern line), to use part of the W&SR's route for an extension of the C&SLR to Sutton.

[2] The Southern Railway (SR) objected, and an agreement was reached that enabled the C&SLR to extend as far as Morden in exchange for the UERL giving up its rights over the W&SR route.

The station opened on 5 January 1930 when full services on the line were extended from South Merton.

All services at St Helier are operated by Thameslink using Class 700 EMUs.