Video: Alexander Litvinenko: poison origins 'a mystery' Former KGB agent Mr Litvinenko was allegedly poisoned by radioactive polonium-210 while drinking tea during a meeting with former security colleagues at the Millennium Hotel in London's Grosvenor Square in November 2006. He died in hospital three weeks later. On Thursday, an inquest heard that he had been working for MI6 before his death. Intelligence analyst Glenmore Trenear-Harvey said that the manner in which the British Government had pursued Mr Litvinenko's alleged killers showed that they probably, "had good reason to believe that this was a hit originating from Moscow and perpetrated by them." He believes that the large quantities of polonium-210 needed to carry out such an assassination "would only come from a government source." He added: "Whether indeed it was provided legitimately by the Russian government who knows?"