i'm a rational man. even if i had taken part in an operation and had known what was in the container would i take my family along? i'm a rational man. i couldn't do it. >> not only did he continue to maintain his innocence he offered his own theory about who poisoned the tea. >> could someone put something in there without you noticing? >> translator: no. why don't you think it could have been put there the next day or from a guy from mi 6. he brings polonium and pours it into the cup? that is agatha christie stuff. >> he says perhaps the brits killed litvinenko to embarrass russia. retired mi 6 analyst says that's nonsense. if for no other reason because mi 6 would never use such an expensive weapon to kill anyone. >> if the british wanted to kill him then he would have fallen