During World War II a bombing decoy town was constructed on Black Down, which was intended to represent the blazing lights of a town which had omitted to follow black-out regulations. The decoy, known under the code name Starfish from the original code SF (Special Fire) used fires of creosote and water to simulate incendiary bombs exploding. In addition glow boxes were used to simulate the streets and railways of Bristol, the light bulbs were powered by electrical generators, powered by Coventry Climax petrol engines contained in two bunkers. It was laid out by Shepperton Film Studios, based on aerial photographs of the city's railway marshalling yards. The decoys were fitted with dim red lights, simulating activities like the stoking of steam locomotives. Burning bales of straw soaked in creosote were used to simulate the effects of incendiary bombs dropped by the first wave of Pathfinder night bombers; meanwhile, incendiary bombs dropped on the correct location were quickly smothered, wherever possible. Drums of oil were also ignited to simulate the effect of a blazing city or town, with the aim of fooling subsequent waves of bombers into dropping their bombs on the wrong location. The site was home to a Z battery of anti aircraft rockets. The success of this endeavour is questionable, with no ground indications that the hills were used as targets. Piles of stones (known as cairns) were also created to prevent enemy aircraft from using the hilltop as a landing site.