Now it is official that Sergei Skripal, the former Russian intelligence officer, and his daughter Yulia were poisoned in Salisbury last Sunday (4th March) by a nerve agent, there is something of a scramble among commentators to unpack what that scary-sounding term means.
Of course, the first thing it means is that Skripal is not a victim of food poisoning or some other accidentally incurred chemical or biological poisoning. As was suspected, given that he is a former spy jailed in Russia in 2006 for counter-espionage and then released in the kind of tit-for-tat swap most of us imagined went out of fashion after the Cold War ended, the poisoning is evidently deliberate. Counter-terrorist officials in the Metropolitan Police say they have identified the nerve agent used but have not yet disclosed what it was.
The BBC was told by an anonymous source that it is rare, however, and so seems unlikely to be the best known agents: sarin—which was used in the Tokyo underground attack by members of the Aum Shinrikyo sect in 1995, and last year by Syrian government forces to attack rebel groups—and VX, which was used to kill Kim Jong-nam, the half-brother of North Korean leader Kim Jong-un, in Malaysia, also last year.