In 2006 Alexander Litvinenko - journalist, Kremlin critic, and undercover MI6 spy - was poisoned in central London. The murder weapon? Polonium: rare, lethal and highly radioactive. His crime? He had made some powerful enemies in Russia.

A Very Expensive Poison traces the journey of the nuclear toxin across London, from hotel room to nightclub, assassin to victim. Along the way, he explores the deaths of other prominent Russians - in exile and at home. He argues that Litvinenko's murder marked the beginning of the crisis in relations between Moscow and the west. With Russia's covert war in Ukraine, its annexation of Crimea, and bombing of Syria, Europe faces a new Cold War, with fewer certainties.

This is a shocking story, with corruption and subterfuge at every turn and walk-on parts from the Russian mafia, the KGB, MI6 agents, dedicated British coppers and Russian dissidents. At the heart of it all is an individual and his family torn apart by a ruthless crime.

Chaired by Oliver Bullough, journalist and author of The Last Man in Russia and Let Our Fame Be Great.