All were built in England in two batches by English Electric; 1200 to 1222 at Dick, Kerr & Company in Preston and 1223–1234 at Vulcan Foundry, Newton-le-Willows in 1958.

The locomotive has the 1Co-Co1 wheel arrangement and is carried on two cast steel bogies, each having three driving axles guided at the outer end by a Bissel truck.

[clarification needed] The locomotive superstructure has a semi-streamlined appearance with a cab behind each nose end compartment.

Between the two cabs is the engine compartment, within which the radiators, the power unit and the control cubicle are mounted.

Upholstered fully adjustable seats are provided for the driver and assistant, the driving position being on the right hand side of the cab.

Warning lights are also provided to indicate wheel slip, blower motor failure, low oil pressure and high water temperature.

Roller bearing axleboxes are fitted throughout: those on the Bissel truck are of the cannon box type.

The locomotive output is controlled by varying the speed of the diesel engine and the field strength of the main generator.

Class leader 1200 is now preserved in the Bulawayo Railway Museum,[3] and 1207 at Sandstone Estates in South Africa.