Todays's newspaper finally named the nerve agent used in Salisbury (and got it wrong).
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It would be hard to get any of them anywhere outside Russia. The only other documented intentional use was by the Russian mafia in 1995
"According to the Kommersant newspaper, Novichok agent was allegedly used in a criminal act in 1995 when Russian mafia assassins poisoned Russian banker Ivan Kivelidi, the head of the Russian Business Round Table,[27] and his secretary."
It's unlikely that the Russian mafia had any direct interest in trying to kill an ex-Russian and his daughter, but they might have been trying to curry favour.