Screening: How to Poison a Spy

Panorama’s investigation into the death of former Russian agent Alexander Litvinenko has found that it is likely there were multiple attempts to poison him with Polonium 210 with the first as early as two weeks before he visited the London Sushi Bar on November 1.

In the documentary Litvinenko’s widow claims that the Kremlin is responsible for Litvinenko’s murder.

She said: "I cannot say exactly that Putin killed my husband but I can say that Putin is behind everything that happens in Russia."

The Kremlin has called Marina Litvinenko a "liar".

President Vladimir Putin’s press spokesman said: "Indirectly she says that Russia has done it. I answer directly that Russia has not done it. It is absurd even to think about it."