Fortunately for Land Rover, this was a period when the military were as keen to buy Land Rovers as Land Rover were to sell to the military. As a result, the two sides formed what was, to all intents and purposes, a design committee made up from Land Rover's engineering department and MVEE (the Military Vehicle Engineering Establishment). In 1966 this committee laid down the parameters for the Army's new Gun Tractor and Land Rover undertook to build prototypes. The initial requirement was for a vehicle capable of towing a 4,000lb artillery weapon (the production 105mm Field Gun actually came in at 4,088lbs / 1,858kg) at speed over rough terrain. The vehicle should also be capable of carrying the six-man gun crew and their equipment, plus driver and passenger. It should be small enough to fit into the RAF's Andover transport aircraft and be light enough for sling-transportation by the latest generation of heavy-lift helicopters.

Nothing in the Land Rover family album could not come anywhere close to matching such requirements, so Norman Busby was appointed Project Engineer and started work in mid-1966 with a blank sheet of paper. In order to achieve the required compactness, a forward control design was settled upon with the driving compartment over the engine. The wheelbase was kept as short as possible, as were the front and rear overhangs - the "brick with a wheel at each corner" design came early. The classic Land Rover-style box-section ladder frame chassis was used, but with straight side members rather than the usual arched curves to accommodate the axles.

The power train was more problematical, as it was clear that this vehicle was going to need all the power and torque it could get. The most powerful engine then available to Land Rover was the 3-litre straight six, detuned from its original saloon car application to give 110bhp at 4,500rpm and 150lb ft at 1,500rpm. This was fed through a near-normal Land Rover four speed box and two-speed transfer box. The then-experimental Lightweight provided the inspiration for the demountable body panel design, even though weight reduction was not the over-riding concern for the Gun Tractor. It was, though, seen to make it more readily adaptable. The first prototype was built up during late 1966 and early 1967, with the first testing prototypes being delivered to the MVEE in the summer. During this period the Army were also looking at alternative vehicles for this role, amongst them the Steyr-Puch Haflinger (the forerunner to the remarkable Pinzgauer that is now in service) and the Volvo 4140.

The early testing of the prototypes raised a number of issues and a number of changes were made. The most important of these was to the power train as the MVEE reported that the vehicle was under-powered with the straight-six engine. Time was, on this occasion, on Land Rover's side as the ex-Buick 3.5 V8 had by now entered production for Rover saloons in 1967 and was already being considered for use in the Land Rover 100-inch Station Wagon (which later became the Range Rover). Better still, this planned application was also developing a new gearbox and transfer box to go with it, so the Gun Tractor team decided to try this new combination out as well. By December 1968 one of the prototypes had been fitted with the new V8 and gearbox. With this new set-up came permanent four-wheel drive, which put less strain on the rear axle and therefore allowed the heavy-duty ENV rear axle to be replaced by a lightweight Salisbury unit. The first installations used the transmission in standard Range Rover form, which resulted in very steep propshaft angles and a similarly steep number of propshaft failures. Shortening of the bellhousing and the first motion shaft allowed the gearbox to be moved further forward and thereby reducing the angles on the rear propshaft. After further general modifications resulting from hot-weather testing in California, the MVEE declared themselves to be satisfied with the 101.

Even so, the 101's development was by no means complete. The 105mm Field Gun was not due in service until 1975, and so had no need for the new purpose-built vehicle until 1974 at the earliest. The intervening period was taken up with experiments with powered trailer drives and adapting the 101 to meet whatever additional role requirements the military came up with. This constant movement of goalposts became particularly irksome for Land Rover, particularly when the Army's delivery requirements are taken into consideration. As the 101 is so different to any other Land Rover, the only way it could be built with any sort of efficiency was to build in large batches on the existing Lode Lane assembly lines. However, the Army wanted to take the 101 in small batches to match deliveries of the 105mm Field Gun. After a great deal of discussion, it appears that Land Rover issued an ultimatum - the Army would take delivery in large batches or not at all. A compromise was reached whereby a handful of vehicles were produced between 1972 and 1974 and the majority were built in large batches between 1975 and 1977, the most intensive year being 1976.

Active Service
The first operational deployment of the 101 came in 1982 as part of the Falklands Task Force. Although it was generally accepted that the islands were unsuitable for wheeled vehicles, a few were taken by the Paras and Commandos - one was even captured on film during the liberation of Port Stanley. Their next large-scale deployment was to Saudi Arabia in 1990-91 where, in their Rapier Missile System Tractor role, they provided the last line of defence for the British troop concentrations preparing to recapture Kuwait. Soon after, a small contingent served with the Royal Marines in Northern Iraq tasked with protecting the Kurds. A small number even made it out to Croatia and Bosnia in the first half of the Nineties, but by the end of 1998 almost all had been withdrawn from service. The last big batch to be released were the ambulance-bodied vehicles; these retired en-masse in 1999.