The British Rail Class 43 (HST) is the TOPS classification used for the InterCity 125 High Speed Train (formerly Classes 253 and 254) diesel-electric power cars, built by British Rail Engineering Limited from 1975 to 1982, and in service in the UK since 1976.
The class is officially the fastest diesel locomotive in the world, with an absolute maximum speed of 148.5 mph (239.0 km/h), and a regular service speed of 125 mph (201 km/h). The record run was led by 43102 (43302) and trailed by 43159.