British Rail Class 309

The British Rail Class 309 "Clacton Express" electric multiple units (EMUs) were built by British Rail (BR) York Works from 1962-1963. They were initially classified as Class AM9 before the introduction of TOPS. These units were the first express 25 kV alternating current (AC) units to be built by British Rail, and British Rail's first EMUs to be capable of 100 mph.