The line from Alton to the main line two miles north of Winchester was opened in 1865.  Although owned by a private company, it was staffed and operated by the L&SWR from the beginning, and the larger company absorbed the line in 1876.  The line was never a great success, although it was used by expresses on occasion if the main line through Basingstoke was unavailable.  Diesel units replaced steam in 1957, providing an hourly service between Alton and Southampton.  Passenger traffic was not sufficient to support the service however, and the line was closed in 1973.

Immediately after closure, local volunteers formed the Mid Hants Railway, and through share issues and other fund-raising, they were able to purchase the track bed.  A steam service from Alresford to Ropley opened in 1977, and the extension to Alton Station was completed in 1985, with the Mid Hants trains using platform 3.  West of Alresford, the station at Itchen Abbas has been demolished for a small housing development, and the M3 severs the old track bed near Winchester, so no westward extension is feasible.  

The stations now on the line are Alton, Medstead & Four Marks, Ropley and Alresford.  The Watercress Line, as it is generally known, is now one of the most successful heritage railways in southern England.