In the first episode of this four part series, Russian dissident Alexander Litvinenko flees Moscow to live in exile in London, but he doesn't know Russian agents are moving against him and there will be no billionaire to protect him.
As Sashais dying of a mysterious illness, time is running out for the police to get crucial information about his attackers. The race is on to find out who poisoned him and why.
The Litvinenko investigation moves to Moscow. If British police want to interview their chief suspects, they'll need to get co-operation from the Russian authorities.
Alice and Matt talk to journalist and author Luke Harding about what The Litvinenko Affair means today. He is the author of A Very Expensive Poison, the Definitive Story of the Murder of Litvinenko and Russia's War with the West.
