Questions have been raised again about Novichok after German authorities saidRussian opposition leader Alexei Navalny was poisoned with the nerve agent.
MrNavalny, one of the most prominent critics of Russian president VladimirPutin, fell ill on August 20 and was transferred to a Berlin hospital wheretests found he had been poisoned.
The Soviet-era chemical came tointernational attention after five people were poisoned in Wiltshire in 2018.
