By Juliet Bremner: ITV News Correspondent
Marina Litvinenko tells the inquiry into her husband's death that she first met one of the prime suspects, Andrei Lugovoy, at businessman Boris Berezovsky's 60th birthday party.
She said that her husband and Lugovoy spoke and exchanged business contacts, but she didn't think the two men had a close relationship.
"Obviously there was not any friendship or any relationship between Sacha and Lugovoy" she told the inquiry.
Marina thought this might be because Sacha was worried he would try to take some of his work with Boris Berezovsky, who paid for the Litvinenko's house and for research done for his international foundation.
She has been telling the court about various business contacts that Alexander or "Sacha" had when he was in the UK. These included two men who helped him to research organised crime in Russia and the Ukraine known only as "Sergei" and "Slava".
Marina was asked if she knew anything about her husband being involved in trying to buy a large amount of copper - she did not.
It has been suggested that Alexander Litvinenko may have been poisoned by the polonium after he had himself been involved in buying the radioactive material.
Marina was asked whether it was possible that he might have tried to buy radio active material. Robin Tam QC asked, "Do you know if Sacha had ever been involved in or was looking into buying any nuclear materials any radio active material?"
She replied, "No, I don't know of any example of this." Marina claimed that her husband would not get involved in any illegal activity in Britain.