The British Rail Class 43 (HST) is the TOPS classification used for the InterCity 125 High Speed Train (formerly classes 253 and 254) power cars, built by BREL from 1975 to 1982.The class is the fastest diesel locomotive in the world, with an absolute maximum speed of 148 mph (238 km/h), and a regular service speed of 125 mph (201 km/h).