Petroleum Warfare Department

By mid-June, as a basic anti-invasion precaution, wayside petrol stations near the coast had been emptied, or at least had their pumps disabled, and garages everywhere were required to have a plan to prevent their stocks being of use to the invader.

Early in July 1940, Banks was summoned to the presence of Geoffrey Lloyd, who explained the vision that Hankey and he shared: "Flame all across Britain" he said, "ringing the coasts, spurting from the hedges and rolling down the hills.

[23] In the defence of Boulogne, a group of pioneers under Lieutenant-colonel Donald Dean VC, had improvised a road block made of vehicles and piles of furniture from bombed-out houses.

This consisted of a number of 12-inch (30 cm) diameter pipes welded shut to make a 12-foot (3.7 m) long cylindrical drum, which was filled with 43 imperial gallons (200 L) of petrol-oil mixture and pressurised with an inert gas.

[32] His best-known invention was the Livens projector: a simple mortar that could throw a projectile containing about 30 lb (14 kg) of explosives, incendiary oil, or most commonly, poisonous phosgene gas.

[f] A barrel of oil was simply 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".

[37] The design was reminiscent of a weapon dating from late 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 leaflet drop never took place, but the exercise prompted Department EH to issue a note to the Air Ministry insisting on the importance of a properly coordinated system for sending information to enemy countries.

Writing just after the war, Banks said, "Perhaps the greatest contribution from all these variegated efforts was in building up the great propaganda story of the Flame Defence of Britain which swept the Continent of Europe in 1940.

This rumour was whispered into attentive ears in neutral cities such as Stockholm, Lisbon, Madrid, Cairo, Istanbul, Ankara, New York, and other places,[56] probably around late July or early August 1940.

It was found that effectiveness was very much affected by sea conditions; a low temperature made ignition more difficult and waves would quickly break up the oil into small ineffectual slicks.

In South Wales long stretches were put in hand at the time when the airborne threat to Ireland was looming large, and sections at Wick and Thurso, but these were not brought to completion.

From about September 1940, 300 Home Guard units received a kit of parts provided by the PWD - a 50 to 65 imp gal (230 to 300 L) barrel, 100 ft (30 m) of hose, a hand pump, some connective plumbing, and a set of do-it-yourself instructions.

The nozzle and ground spike were of simple construction from sections of three-quarter-inch-diameter gas pipe with a used food can over the end to catch drips of fuel that would maintain a flame when the pressure was allowed to drop.

[95] It comprised a welded-steel cylinder containing 22 gallons (100 L) of creosote and a standard bottle of compressed nitrogen at 1,800 pounds per square inch (120 bar) mounted on a sack truck of the type that a railway-station porter might use.

[96] Like the Home Guard flamethrower, it was intended as an ambush weapon, but in this case the operator was able to direct the flames by moving the lance which would be pushed through a hole in otherwise bulletproof cover such as a brick wall.

[103] Reginald Fraser of Imperial College, London University, who was also a director of the Lagonda car company, developed an annular flamethrower, that threw petrol with an outer layer of thickened fuel.

[104] A demonstration of the Lagonda vehicle at PWD's test site at Moody Down farm near Winchester was attended by Nevil Shute Norway and Lieutenant Jack Cooke of the Admiralty Directorate of Miscellaneous Weapons Development.

An experiment with a Cockatrice-like flamethrower on board La Patrie, the flame's length was increased by the up-draft of the heat generated so that the pillar of fire reached 300 ft (91 m) vertically.

[117][119] Early in August the specification was settled and put in hand by Logondas and in November it was careening about the Moody Downs, ridden cowboy fashion by Canadians with the governors off the engines.

[116] Work began on two prototypes based on the Valentine tank, both had fuel stored in a trailer but each employed a different system for generating the gas pressure required for the flame projector.

[134][135] The first prototype was completed early in 1942 and a report by the Royal Armoured Corps stated that the Crocodile was not a requirement of the General Staff but that PWD was hoping that a demonstration in the near future would change minds.

[149] Hartley proposed a scheme using adapted underwater power cable developed by Siemens Brothers, (in conjunction with the National Physical Laboratory) was adopted[150][2] and it became known as the HAIS pipeline.

[145] The design of HAIS was refined as a result of a series of tests, the main changes being to increase the layers of steel tape armouring from two to four[152] and to manufacture the inner lead pipe using extrusion thereby avoiding a longitudinal seam.

[153] In March 1943, in a full-scale feasibility test, HMS Holdfast laid a pipeline between Swansea and Ilfracombe, a distance of about 30 miles (48 km); the pipe supplied North Devon and Cornwall with petrol for over a year.

[182] Near the shore the pumps were installed in the remains of the Royal Spa Hotel "simulating on a new elevation – twelve feet higher up the debris and wrecked dwelling-rooms – even the contents of the bathrooms, that strewed the ground, and hiding our mechanisms beneath this false floor.

[202] These short lengths were sent to Swansea where the recovered lead was melted and cast into ingots; the wires were straightened and used as rebars; the steel tapes were flatted and used to make corner reinforcements for heavy duty cardboard boxes; and the jute was made into blocks that could be burned as fuel in a furnace.

Eventually, in September 1941 Charles Portal, Chief of the Air Staff and Lord Cherwell, Churchill's scientific advisor, recommended that the pre-war fog dispersal work should be resumed.

Lloyd visited fruit farmers who used Smudge pot heaters to protect their crops;[207] Hartley arranged for a part of the King George VI Reservoir that had been left empty for the duration of the war to be used for experiments;[207] and Walker took to long walks on foggy nights wearing a government issue donkey jacket – much to the puzzlement of his family.

[22][223] Newsreels told the British public how flamethrower weapons had been developed to defend the country against invasion[224][225] and how the PLUTO and FIDO projects had helped win the war.