The 26 locos are nearly identical to the more numerous Class 08 shunting locomotives but have different gearing, giving a higher top speed of 27.5 mph (44 km/h) at the expense of a lower tractive effort. They were introduced from 1959 to 1962 and latterly operated in the Southern Region of British Railways, although some of the class were originally allocated to depots in the Midlands and North. Further locomotives were converted from Class 08 in 1992 and, following this and privatisation in 1997, the class has been distributed much further afield.