Development and Use in War: (4) Britain: It may only stop it for two minutes there, but it will be quite effective. Wintringham advised that a tank that was isolated from supporting infantry was potentially vulnerable to men who had the required determination and cunning to get close. Rifles or even a shotgun would be sufficient to persuade the crew to close all the hatches, and then the view from the tank is very limited; a turret-mounted machine gun has a very slow traverse and cannot hope to fend off attackers coming from all directions. Once sufficiently close, it is possible to hide where the tank's gunner cannot See: "The most dangerous distance away from a tank is 200 yards; the safest distance is six inches". Petrol bombs will soon produce a pall of blinding smoke, and a well-placed explosive package or even a stout iron bar in the tracks can immobilise the vehicle, leaving it at the mercy of further petrol bombs which will suffocate the engine and possibly the crew or an explosive charge or anti-tank mine. By August 1940, the War Office produced training instructions for the creation and use of Molotov cocktails. The instructions suggested scoring the bottles vertically with a diamond to ensure breakage and providing fuel-soaked rag, windproof matches or a length of cinema film (made of highly flammable nitrocellulose) as a source of ignition. On 29 July 1940, manufacturers Albright & Wilson of Oldbury demonstrated to the RAF how their white phosphorus could be used to ignite incendiary bombs. The demonstration involved throwing glass bottles containing a mixture of petrol and phosphorus at pieces of wood and into a hut. On breaking, the phosphorus was exposed to the air and spontaneously ignited; the petrol also burned, resulting in a fierce fire. Because of safety concerns, the RAF was not interested in white phosphorus as a source of ignition, but the idea of a self-igniting petrol bomb took hold. Initially known as an A. W. bomb, it was officially named the No. 76 Grenade, but more commonly known as the SIP (Self-Igniting Phosphorus) grenade. The perfected list of ingredients was yellow phosphorus, benzene, water and a two-inch strip of raw rubber; all in a half-pint bottle sealed with a crown stopper