The Class 66 is a type of six-axle diesel electric freight locomotive developed in part from the Class 59, for use on the railways of the UK. Since its introduction the class has been successful and has been sold to British and other European railway companies. In Continental Europe it is marketed as the EMD Class 66 (JT42CWR). Placing what was termed as "the biggest British loco order since steam days," EWS placed an order for 250 units in May 1996 to be built at the EMD plant in London, Ontario, Canada; the first locomotives were ready in 1998. They were given the Class 66 designation in the British classification system (TOPS). In 1998 Freightliner placed an order for further locomotives. They were followed by GB Railfreight, and then Direct Rail Services. The last of more than 500 built over an 18-year period was No 66779, Evening Star, delivered to GB Railfreight in spring 2016.
Class 66 is synonymous with the contemporary UK rail scene, operating for all the major freight operators including DB, Freightliner, GB Railfreight, Colas Rail, and DRS, and they are set to dominate the domestic locomotive fleet for many years to come.