British Rail Class 707

The Class 707 is an electric multiple unit being built by Siemens for South West Trains. A total of 150 vehicles will be built, formed into 30 x 5-car units, and are being built to provide initially for 18,000 additional peak-time passengers into London Waterloo, with a further 6,000 additional passengers capable of being accommodated on completion of associated infrastructure improvements.

History
In September 2014 South West Trains announced plans to procure a total of 30 five-car trains as a means of expanding the fleet used to operate services out of London Waterloo. As a result of significant infrastructure improvements to allow the operation of 10-car trains across large parts of the SWT network, the operator procured significant amounts of additional rolling stock to allow for this. SWT's fleet is largely up of Desiro units built by Siemens, and the Class 707 will be a follow on of this, as the second product purchased for use on the British network from the Desiro City range (following the purchase of the Class 700 for Thameslink).

Operation
The Class 707 units are intended primarily for services between London Waterloo and Windsor, allowing the Class 458 trains used on those services to be cascaded back to operations to Reading, which will then allow the Class 450s to move elsewhere. The intention is to run these services, as well as others via Staines, and some mainline services to Basingstoke, as ten-car trains with pairs of Class 707s.

The Class 707 units are planned to be based at SWT's Wimbledon Traincare depot.