Famed for their own 'HHT' trucks, these heavy tractors were custom built to the company's requirements, and 4 were built. Using the chassis and axles from Scammell contractor, a Detroit 8V92 was shoehorned under the bonnet, mated to Fuller gearbox and 4 speed auxiliary. A Volvo F88/F89 cab was used. The exception was HHT OO4, which used a Caterpillar 3406 engine. In later years, several F16 Volvo's were converted to 4 axle ballasted tractor configuration, for operation at up to 200 tonnes combination weight.