The British Rail Class 89 is a prototype electric locomotive. Only one was built, in 1986, by British Rail Engineering Limited's Crewe Works. It was used on test-trains on both the West Coast and East Coast Main Lines. The locomotive was fitted with advanced power control systems and developed more than 6,000 bhp (4,500 kW). After being withdrawn in 1992, it was returned to service in 1996, before being again withdrawn in 2000. As of January 2021, it is in the final stages of an overhaul that will return it to the main line. Design The Class 89 locomotive was designed by Brush Traction, Loughborough to meet a specification issued by British Rail. BR subsequently changed the requirements of this specification, but not before Brush had committed to building the prototype locomotive. The locomotive has six DC traction motors. The main armature current for all the motors is fed from a common thyristor drive, with each motor having an independent field current controller. The field current controllers comprise a two quadrant chopper inside a thyristor bridge. The bipolar transistor based choppers provide a fast fine control of motor torque for electric braking and slip control, while the thyristor bridge is used to invert the field current polarity. History The specification for the locomotive was laid out in mid 1981, which then went out to tender in April 1982. The contract to build the locomotive was awarded to Brush in June 1983, with BREL Crewe as the nominated subcontractor and delivery planned for September 1985. The locomotive was built at British Rail Engineering Limited's Crewe Works in 1986, emerging and being initially delivered to Derby Litchurch Lane Works on 2 October 1986. The Class 89 was then transferred by road to Brush Traction at Loughborough for static testing and commissioning. It was initially delivered in the old-style InterCity Executive livery, with no British Rail double arrows, but these were added later when British Rail bought the locomotive from Brush. The locomotive was taken to Crewe Electric TMD on 9 February 1987. The following day, it first ran under its own power, inside the depot perimeter. The first lone run on the mainline was on 20 February 1987. On 6 March 1987, the locomotive visited the Railway Technical Centre for weighing and other tests. 89001 was moved to the Old Dalby Test Track for evaluation and pantograph tuning on 13 April 1987.