When a passenger check-in desk at Terminal Two, Heathrow Airport, shot up through the roof engulfed in a ball of orange flame, the usual people tried to claim responsibility. First the IRA, then the PLO and the Gas Board. Even British Nuclear Fuels rushed out a statement to the effect that the situation was completely under control, that it was a one in a million chance, that there was hardly any radioactive leakage at all and that the site of the explosion would make a nice location for a day out with the kids and a picnic, before finally having to admit that it wasn't actually anything to do with them at all.No rational cause could be found for the explosion - it was simply designated an a