David Tennant says Putin tried to silence poisoned Russian he plays on Litvinenko : 'He failed'

In the based-on-real-events crime drama Litvinenko, David Tennant plays the title role of Alexander "Sasha" Litvinenko, a Russian-born critic of President Putin who was fatally poisoned in London during the fall of 2006.

"It's the story of Alexander Litvinenko, who is admitted to hospital with a very mysterious and terribly fast-moving medical condition," explains Tennant. "The only person who knows what it is, is Alexander Litvinenko himself who says he's been poisoned. He says he knows this because he used to work for the Russian secret service, the FSB, and this is how they get rid of people they don't like. Two officers from Scotland Yard come, and decide to take a chance in believing him, and start to take his statement, and it turns out that everything he's saying is true. He's fled Russia, and has been telling anyone who wants to hear ever since that Putin is at the head of a very corrupt regime, and needs to be stopped."

Tennant's Litvinenko is essentially the sole witness to his own murder.

"Because he manages to live on for a number of days, they find that he is in fact poisoned by something called Polonium 210, which is this extraordinarily rare isotope," says the Doctor Who star. "Then it becomes the story of the police investigation, how they tried to join the dots, and prove that what Sasha himself claimed on his death bed was true, and that he was a victim of state-sponsored assassination."

ITVX/Sundance Now David Tennant in 'Litvinenko'

The four-part AMC+ and Sundance Now show was made with the support and cooperation of Litvinenko's widow, Marina, who is played on the show by Margarita Levieva.

"Marina is so open and she so generously shared all her experience and it's still so raw to her, of course," says Tennant. "This is not the life that she imagined for herself and yet her persistence and her quiet strength is something to be marveled at. She really is the inspiration for all of us who made this show — and her support and her enthusiasm and her accessibility, I can't imagine what it would have been without that. She would say herself, she's dedicated her life to making sure this story is out there. She does not want Sasha's life to have been in vain. And that's what Putin wanted. Putin wanted to shut him up and he failed on that front."

ITVX/Sundance Now Temirlan Blaev, David Tennant, and Margarita Levieva in 'Litvinenko'

Tennant's portrayal of Litvinenko mostly takes place on what would tragically turn out to be his deathbed. What was it like filming those sequences?

"It felt very precious," he says. "It felt like we were carrying something very precarious, that we had to look after, and be as respectful towards, and as truthful towards, as we possibly could be. Margarita was just extraordinary because she just became Marina. I know they spent a lot of time together, I think they continue to spend quite a lot of time together, and there were moments when I'd be in the hospital bed, and I'd look up, and Marina seemed to be there, fully realized, in Margarita's performance. You know, she physically became her. She really went to some very difficult places, she did not shy away. I think it really counts. I just think it's such an important story to tell. The repercussions continue, and the story of Putin continues, and where that will end, lord alone knows."

All episodes of Litvinenko will debut Dec. 16 on AMC+ and Sundance Now. Watch an exclusive clip from the show below.

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