The tractor is a highly modified version of the standard 95 bhp Fowler Challenger III diesel crawler tractor, manufactured by John Fowler & Co. of Leeds.

[1] A prototype was trialled successfully at Aberystwyth in 1952[2] The tractor developed a draw-bar pull of 21,100 Lbs, through its six-speed gearbox, and was fitted with a specially designed winch, allowing it to exert a maximum pull of 38,500 Lbs.

Extended gear and clutch levers were fitted, to assist the driver when submerged.

Circular brass rubber-seated valves were fitted to the air intake and discharge ports, to be closed when submerged.

To prevent damage, an automatic stop device was also employed.