Class 57 is the result of a collaboration between Brush of Loughborough and Porterbrook, creating a new locomotive from an old one, the Class 47. The major change was the fitting of a General Motors engine for greater reliability and reduced overhaul costs. Porterbrook commissioned the first Class 57, 57601 which proved very successful and brought about orders from Freightliner (Class 57/0) and Virgin (Class 57/3). The 57/3 locomotives are fitted with Dellner couplers for hauling Pendolino trains when no overhead power supply is available. These are also “rescue” locomotives, hence their name “Thunderbirds”, the name used by “International Rescue” in the Gerry Anderson TV series. The 57/3 uses a 645-F3B 12 Cylinder engine, allowing a 95mph top speed and an ETH index of 100. Other work carried out at the refurbishing was re-wiring, new main and auxiliary alternators, new cooler group, new silencer, fault diagnosis system fitted, cab environment improved, bogies overhauled and, of course, a new livery.