Claims are surfacing in press reports today that two Russians charged by the UK government for the Novichok nerve agent poisonings in Salisbury were carrying enough of the stuff to kill 4000 people.

Given that only Russia is known to have a stockpile of Novichok agents , the suspicion levelled at the Russians seems reasonable. But could they really have killed thousands?

Claims like this are regularly made about chemical and biological weapons, which are usually lumped together as weapons of mass destruction (WMDs) although they are quite different – …