Never before has a British wind energy story excited so much debate and speculation. The idea that aliens might be responsible for damage to the rotor of a wind turbine in Lincolnshire, east England, last month captured the public's imagination worldwide. "UFO hits wind turbine," "UFOs spotted by hundreds at wind turbine site," and "Strange lights reported as wind turbine damaged," were just some of the headlines that fuelled the mystery of why one rotor blade snapped off and another was badly damaged on a single turbine at Ecotricity's Fen Farm wind farm at Conisholme. While the story led to a spate of UFO sightings throughout the UK, other theories emerged. Defence aircraft activity, a meteorite, falling ice and even flying cows were all considered as possible culprits. More prosaic explanations were put forward too: the mysterious lights were explained away as fireworks, while lightning and mechanical failure were cited as possible causes of the damage. From Ecotricity, however, Dale Vince says that ice and lightning have been ruled out. That leaves collision, although there is no evidence on the ground, he says, or materials or maintenance failure. The damaged blades have been sent back to manufacturer Enercon for "forensic" testing. All three blades will be replaced, including the third blade that appeared undamaged, says Vince. "To be honest we had a lot of fun with this and that took the edge off what was otherwise a serious and very bad event for us."