"From the mid 1930's re-armament of the British forces started and Crossley again became heavily involved with its previous customer the Royal Air Force. As the number of RAF squadrons grew so did the need for ground transport and this was at first satisfied by the IGL3 petrol engined truck with over 700 being supplied. In 1935 a new War Office specification was issued for a medium 3 ton 4 x 4 truck that was to replace the 6 x 4 IGL type and in 1938 an order for a prototype was placed. This vehicle was of an advanced design with independent suspension, the new 38/110 bus engine and a 5 speed gearbox. It performed well but in the end because of pressures to get production underway and ease of repair the War Office requested a simpler vehicle. The final design, known as the FWD or Four Wheel Drive, had an 11 foot wheelbase and used a conventional suspension, the drive train of the 2 axle IGL and the proven 30/70 engine. The name often used for these, the Quad or "Q" type, is not strictly correct as "Q" was the specification title used by the War Office and so could be applied to vehicles from several manufacturers of differing designs.
Just after the outbreak of war in 1939 production of the FWD started in earnest with initial orders for 506 trucks and 228 crash tenders, and a further 700 vehicles after the British Expeditionary Force lost most of its equipment in the 1940 retreat to Dunkirk. First deliveries were in July 1940 and nearly 800 were delivered by the end of the year along with 340 IGL's. In 1943 a tractor variant entered production and a more powerful 96bhp (later 100bhp) engine, the 30/100, available as an option. Three variants in all were produced known as Types 1, 2 and 3 with differences in transmissions and engines".
A photo of a RAF FWD I found, late-war. looks rather like the trials truck! Another mystery solved?