Parallel development work was carried out by the Petroleum Warfare Department, AEC and the Ministry of Supply (MoS) on Valentine tanks.

[1] The General Staff decided a flamethrower based on the Churchill using the Petroleum Warfare Department's design was required.

[2] War Office policy reversed this decision in August 1942; tanks were thought to be too vulnerable at close range and the flamethrowers should be manpack or Carrier types.

[4] After Major-General Percy Hobart saw the Crocodile demonstrated in 1943, he put pressure on the MoS to produce a development plan.

[5] A Royal Armoured Corps advisor to the General Staff Major-General Alec Richardson was shown the prototype in January 1943 and it was also demonstrated for the War Office in March.

[9] The conversion kit consisted of the trailer, an armoured pipe fitted along the underside of the tank, and the projector, which replaced the hull-mounted Besa machine gun.

The Crocodile's six and a half ton armoured trailer carried 400 imperial gallons (1,800 L) of fuel[11][page needed] and five cylinders containing compressed gas propellant.

To make the task easier, it was common to construct an elevated structure of scaffolding poles that allowed the drums to be rolled out of the truck that delivered them to a position over the trailer, so the fuel could be poured straight in.

[15] For transport over long distances, Crocodile units were issued with AEC Matador lorries to tow the trailers.

Used by units of the 79th Armoured Division in concert with the Churchill AVRE, and other Funnies, the Crocodile was an effective assault weapon, used so successfully against bunkers that many surrendered after the first ranging shots.

The flame projector was a powerful psychological weapon, so feared by the Germans that captured Crocodile crews were often summarily executed.

[25][26] Aspects of the mechanism were considered by the British to be so secret that disabled units, if they could not be recovered, were rapidly destroyed by any means, even air strike if necessary.

[27][page needed] British Crocodiles supported the U.S. Army in the Normandy bocage, at the Battle for Brest, and during Operation Clipper, the Anglo-American assault on Geilenkirchen.

[29][page needed] From late 1950 until their withdrawal in 1951, Churchill Crocodiles served in Korea as part C Squadron, 7th Royal Tank Regiment in 29th Brigade.

After heavy use of both their flame projecters and their main guns, the tanks were able to force the German defenders to abandon the fortress.

Another, complete with a trailer, is on display on Fort Montbarey parade ground in Brest (Brittany); it was given as a Memorial by Queen Elizabeth II.