From the 1920s, petrol, and later, diesel tractors gradually replaced steam traction engines in heavy haulage. Scammell Lorries, Watford (established 1922) was deeply involved in the development of articulated, heavy haulage and cross-country vehicles. The Scammell Pioneer, originally designed for oilfield work and driving on all six wheels, was adapted as a World War Two military support vehicle. After 1945, demobilised examples were used in heavy haulage or towing and recovery work.

A civilian Pioneer, rated as an 80-ton tractor, was built after 1945. Its 1950 successor, the Constructor, was followed in 1957 by a four-wheel drive Junior Constructor. Essie - named from its fleet number SC1, is of this type. While regarded as a standard model, most heavy-duty Scammells were, effectively, one-offs.

Delivered as a chassis with a crew cab for £11,650 (€14,792), Essie was bodied at CIE’s Spa Road Works and registered on 27th January 1965. It was nominally intended to haul a trailer carrying a 100-ton load, but Scammell ratings were extremely conservative, much heavier consignments being frequently handled.

Special trailers were matched to loads and loaned around among the various users. For exceptional loads, two or three tractors were used. In Ireland, operators of big Scammells included the ESB and Ulster Transport (later Northern Ireland Carriers). Co-operation between such operators ensured that the requisite number of tractors could be brought together when required. Essie was withdrawn in 1986 and is maintained in working order.