History

The FV 620 Stalwart, commonly referred to as the "Stolly", was a robust, amphibious, six-wheeled military transport truck built by Alvis in the 1950s and officially entered service with the British Army in 1966.

The Stalwart was an independent project developed by Alvis, later selected for service with the British Army as a general-purpose transport vehicle, surpassing the FV431, the cargo-carrying model of the FV430 series. It belonged to the same family of vehicles as the Alvis Saracen, Saladin, and Salamander. Its exceptional mobility and amphibious functionality made it particularly well-suited for delivering supplies to units in the field.

Description

The Stalwart’s chassis houses a Rolls Royce B81 MK 8B eight-cylinder engine beneath the rear load deck, with gearboxes and differentials positioned forward. The open-topped load deck features large, drop-down side panels sealed to prevent water leakage. The three-man cab, accessible only through roof hatches, has the driver centrally seated with a passenger on each side.

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Designed to transport up to 5 tonnes of cargo or tow 10 tonnes, the Stalwart is amphibious, using water-jet propulsion to travel at around 6 knots. However, its complex drivetrain—including all-wheel drive, multiple gearboxes, and water propulsion units—required extensive maintenance in service. When amphibious capabilities were unnecessary, the water jets were often removed to reduce upkeep.

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Its 6-wheel-drive system, lacking differentials, relies on bevel gears and a central no-spin differential to maintain traction. This gives the vehicle excellent off-road performance. However, forcing all wheels to rotate at the same speed led to transmission ‘wind up,’ causing wear and breakage on firm surfaces like tarmac. To counter this, military crews used railway sleepers or kerbstones to relieve stress on long road moves.