Lawyer Ben Emmerson, acting for Litvinenko's widow Marina, told the hearing that Litvinenko was working for the British intelligence service MI6 and had been tasked by MI6 with working also for the Spanish intelligence service as it investigated Russian mafia activities in Spain.

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Litvinenko's wife Marina and their 12-year-old son Anatoly were among the mourners, PA said.

CNN: Wife, 50 friends at ex-spy funeral

Maya Sikand, for Mr Litvinenko's widow Marina, said if the Russian state could not become an interested party, it was possible the FSB could.

BBC: Alexander Litvinenko inquest 'may look at MI6 role'