
The thickened fuel gave better performance in terms of range and effect on the target.

The PWD continued with development work of a trailer and equipment including improvements in the fuel. 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. Twelve pilot models were ordered in July 1942. The specification was for a minimum of a minute of flame with an effective range of 80 yards and the fuel to be in a jettisonable trailer. The main armament of the tank was to be retained. The General Staff decided a flamethrower based on the Churchill using the Petroleum Warfare Department's design was required. The Department of Tank Design preferred the Churchill, which was the Infantry tank successor to the Valentine, as a basis for further work.

Parallel development work was carried out by the Petroleum Warfare Department, AEC and the Ministry of Supply (MoS) on Valentine tanks. The Churchill Oke, a flamethrower carrying Churchill Mark II developed by a Royal Tank Regiment officer, was tested operationally on the Dieppe Raid. From early in the war, there had been experiments with mounting flamethrowers on British vehicles leading to vehicles such as the Cockatrice, Basilisk and the Wasp (the latter being a flamethrower on a Universal Carrier).
