The British Railways Standard Class 4 tank is a class of steam locomotive, one of the BR standard classes built during the 1950s. They were used primarily on commuter and outer suburban services. They were capable of reaching speeds of 75 mph (113 km/h).
The Standard 4 tanks were originally allocated to all regions of British Railways, bar the Western. They became particularly associated with the London, Tilbury and Southend line (LT&S) working commuter services out of London, until that route was electrified in 1962. They were also widely used in East Sussex and Kent, working from Brighton, Tunbridge Wells and Three Bridges on those lines of the former London Brighton and South Coast Railway that were not electrified. Another group worked from Polmadie depot in the Scottish region on the Glasgow commuter services. Note that, from July 1962, a batch displaced by electrification of the LT&S was transferred to the Western Region's Swansea (East Dock) and Shrewsbury districts, as well as other regions.