The Electro-pneumatic brake system on British railway trains was introduced in 1950 and remains the primary braking system for multiple units in service today. The Southern Region of British Railways operated a self-contained fleet of electric multiple units for suburban and middle distance passenger trains. From 1950, an expansion of the fleet was undertaken and the new build adopted a braking system that was novel in the UK, the electro-pneumatic brake in which compressed air brake operation was controlled electrically by the driver. This was a considerable and successful technical advance, enabling a quicker and more sensitive response to the driver’s operation of brake controls.