In August 1977, Vickers produced a design for a vehicle that incorporated Chobham composite armour protection within a battle weight of 43 tonnes.
This first prototype, designated the Vickers Main Battle Tank Mark 4, mounted the L7 105 mm rifled gun and, in 1978, underwent automotive tests with the Rolls-Royce CV12 TCA developing 1000 bhp and with the General Motors Detroit Diesel 12V-71T developing 915 bhp.
By the time of the British Army Equipment Exhibition in June 1982, the tank had undergone extensive testing with the new turret.
From February to March 1983, the Valiant took part to the Floater '83 floating arms exhibition, touring the Middle East countries on the ferry Viking Venturer.
The Valiant went back to the Middle East in July and August of the same year where it was involved in desert trials in the United Arab Emirates along the British FV4030/4 Challenger 1 and the French AMX-40.
The sight was monocular, with a magnification of ×10, and was fitted with a Barr and Stroud LF 11 Neodimium-YAG laser rangefinder and a cathode-ray tube for injection of fire-control data.
This was mounted in the turret roof and provided a ×1 wide angle field of view and was used for surveillance and target acquisition.
In addition, a gyrostabilised panoramic thermal sight, the Dutch Philips-USFA UA 9090, was also mounted on the turret roof, in front of the loader's hatch.
The turret structure was made of welded steel plates, with a layer of Chobham armour added to the front and sides.
[i] In addition, however, Chobham armour was also applied along the full length of the hull sides (heavy ballistic skirts).
The first prototype was armed with a Royal Ordnance L7 105 mm rifled gun, 56[3] to 60[2] rounds are carried, 30 of which are stowed in the hull, to the left of the driver.
The L11A5 was fitted with an experimental rigid thermal sleeve optimized for hot weather operations, it was made of a new material called Fibrelam, it was also featured on the Vickers Mk.
The all-mechanical transmission has the inherent advantage of being more efficient, which means that more of the engine power is available to drive the tank, instead of being dissipated by oil coolers.
At the same time, the skill and effort generally required of drivers by mechanical transmissions are eliminated by the electrical controls.
The secondary torsion bars provide more effective springing at the most critical wheel stations and significantly improve the ride over rough ground.