|Type Heavy rail|
|System National Rail|
Owner Network Rail
|Locale Greater London
South of England|
Rolling stocks British Rail Class 319, British Rail Class 377, British Rail Class 455
Terminis Streatham railway station, London Borough of Sutton
The Sutton Loop Line, also known as the Wimbledon Loop, is part of Thameslink and is the circular route formed where the St Helier line diverges from the Portsmouth Line at Streatham South junction and rejoins it near Sutton station. The Sutton Loop includes the historic Surrey Iron Railway stations of Hackbridge/Carshalton, which was the first Iron Railway in the world, following the course of the river Wandle to the Thames. Trains leave southwards from Streatham to enter the loop and then return going northwards. The short section between West Sutton station and West junction is known as the "Wall of Death", possibly due to the very steep concrete walls to the cutting on both sides and the sharpness of the curve which resemble the motorcycle ride at a funfair.
In a clockwise direction round the loop, the stations are:
Traction current is supplied at 750 volts DC via the Third Rail. The supply for this is overseen by Selhurst Electrical Control Room. Signalling is Track Circuit Block with multiple aspect colour light signals, controlled by Victoria Southern Power Signal Box. The line is double track throughout, except where a short bi-directionally signalled single line section passes through Wimbledon station platform 9. Originally the Down St Helier Line used platform 10 at Wimbledon, but this is now used for the Croydon Tramlink terminus which currently comprises a single platform at the southern end, split into two sections so two trams can be held at the same time.
Thameslink runs services from Luton and St Albans, via Blackfriars round the loop. Clockwise services are described as "Sutton via Mitcham Junction" and anti-clockwise as "Sutton via Wimbledon". Additionally during service disruption or when the core section of the Thameslink route is closed, Thameslink Sutton Loop services start and end at London Bridge low level station.
Recent proposals were to increase the frequency of the Thameslink service but terminate at Blackfriars. This would allow the trains through the core section to be replaced with longer trains which could not use the loop, but this has not proceeded due to objections from loop passengers about the withdrawal of their through service.
Southern runs a peak service round the loop (clockwise in the morning peak, anticlockwise in the evening peak) from London Bridge low level. It also runs regular services along the route between Sutton and Mitcham Eastfields.