PUMPING in gas may well have been the least worst option available to the Russian authorities last weekend. Unspeakable threats can necessitate unspeakable remedies, and who can say how many would have died had the siege continued. What is clear is that, for all the hype surrounding non-lethal weapons research, nobody is even close to discovering a fast-acting gas sedative that does not have an unacceptable mortality rate.

The Russians, it can be safely assumed, have been working on such agents for decades. Yet the best they could muster was a gas that killed nearly 20 per cent of the innocents they were trying to free. As New Scientist went to press, Russian officials were still refusing to say what was in the gas. Evidence, however, was beginning to point to the key ingredient being a derivative of fentanyl, a powerful synthetic opiate that has been used as a painkiller ...