[7] Among many ideas, Hankey "brought out of his stable a hobby horse which he had ridden very hard in the 1914–18 war – namely the use of burning oil for defensive purposes.

[8] On 5 June, Churchill authorised Geoffrey Lloyd, the Secretary for Petroleum to press ahead with experiments with Hankey taking the matter under his general supervision.

The Livens Projector was a large, simple mortar that could throw a projectile containing about 30 pounds (14 kg) of explosives, incendiary oil or, most commonly, poisonous phosgene gas.

The great advantage of the Livens Projector was that it was cheap; this allowed hundreds, and on occasions thousands, to be set up and then fired simultaneously catching the enemy by surprise.

A barrel of oil was blown up on the beach; Lloyd was said to have been particularly impressed when he observed a party of high-ranking officers witnessing a test from the top of a cliff making "an instantaneous and precipitate movement to the rear".

[10] The work was dangerous; Livens and Banks were experimenting with five-gallon drums in the shingle at Hythe when a short circuit triggered several weapons.

[9] The experiments led to a particularly promising arrangement: a forty-gallon steel drum[nb 2] buried in an earthen bank with just the round front end exposed.

[1] The design was reminiscent of a weapon dating from post-medieval times called a fougasse: a hollow in which was placed a barrel of gunpowder covered by rocks, the explosives to be detonated by a fuse at an opportune moment.

The safety fougasse was constructed as follows: a small section was excavated from the side of a slope, leaving a shallow platform of earth, and a barrel of incendiary mixture was placed horizontally in a low position with one round face pointing towards the target.

[19][21] The propelling charge was prepared with an electrically triggered detonator in a primer bound with insulating tape to three or four cartridges of ammonal explosive.

To activate the device, the propelling charge was lowered down the pipe and tamped down with dry soil before being connected to a firing point about 100 yards (91 m) away.

Instructions for several variants of this design were published but this construction increases the hazard because the leads would have to be left exposed on the surface and any electrical current applied could, theoretically, ignite the charge.

[1] Banks records that installing the charge only when there was clear danger relatively close at hand was a safety feature required to protect the public from accidents.

Even though the charge was packed into a rubber bag in a tin and sealed with insulating tape, it would not have been a good idea to store it for long in the damp conditions of a flame fougasse installation.

The flame fougasse would offer instant and horrific wounds to any unprotected men caught in its fiery maw and would cause a vehicle engine to stop within seven seconds simply because it was deprived of oxygen (although it would easily start again once the fireball subsided, provided nothing was damaged).

Left on its own at a roadside, in the open and with no attempt at disguise other than to hide the firing wires, it was indistinguishable from the barrels of tar commonly used in road repair.

[33]Placing the hedge hopper so that it worked properly proved difficult to get right and the War Office discouraged its use in favour of the more conventional flame fougasse installation.

[4] In all 50,000 flame fougasse barrels were distributed of which the great majority were installed in 7,000 batteries, mostly in southern England and a little later at 2,000 sites in Scotland.

[36] Although the flame fougasse was never used in Britain, the idea was exported to Greece by a couple of PWD officers when, in 1941, German invasion threatened.

Fougasse flame throwers comprised a cylinder containing a few gallons of petrol and oil; this would be hidden, typically by being buried.

[39] The German version, the Abwehrflammenwerfer 42, had an 8 imperial gallons (36 L; 9.6 US gal) fuel tank and were wired back to a control point from where they could be fired individually or together.

Such weapons are improvised from available fuel containers combined with standard explosive charges or hand grenades and are triggered electrically or by lengths of detonating cord.