Grief-stricken and enraged, Litvinenko's father, Walter, spoke to reporters through a translator. "My son died yesterday and he was killed by a little tiny nuclear bomb. It is so little, so small you couldn't see it," he said.
In a statement Litvinenko dictated to a friend a few days before his death, he left no doubt about who he thought had planted the bomb.
"You may succeed in silencing one man, but the howl of protest will reverberate, Mr. Putin, in your ears for the rest of your life," the statement read.
Marina Litvinenko didn't care about any howl of protest. She was just interested in who had killed her husband, and she believes the president of Russia was involved.
In one way or another, Marina Litvinenko says the Putin government is "absolutely" responsible for her husbands death. "And everything that happened now is dependent of president. And I believe it couldn't happen without his notice."
"Couldn't happen without his knowledge?" Simon asks.
"Yes, Knowledge. Yes, I can't say it's his order, but without his knowledge, it couldn't happen," she claims.
Putin has denied these allegations, but Litvinenko has been on Putin's radar since 1998. Putin ran what is now known as the FSB, formerly the KGB. Litvinenko was a loyal agent who investigated organized crime and corruption in Russia.
But then Litvinenko and several colleagues denounced the intelligence agency for corruption.
At a press conference in Moscow, the dissident agents all disguised themselves – that is, aside from Litvinenko. But Litvinenko's daring landed him in jail. When he was released in 2000, he fled from Moscow with Marina and their son Anatoly. Once in London, Litvinenko became a vocal critic of the intelligence agency and its infamous ruthless methods.
"When he got to England, did you expect him to continue his political activities here?" Simon asks billionaire Boris Berezovsky, Litvinenko's backer
"Yes, from the beginning," Berezovsky says.
Berezovsky supported Litvinenko in London with money, a house, and an appetite for negative information on the Putin regime. Over the years, Litvinenko publicly accused Putin and his intelligence agency of several acts of terrorism; most recently the assassination of a prominent investigative reporter in Moscow, this just weeks before he was poisoned.
"It was absolutely clear for me that he is strong fighter against of regime. He has his clear understanding that regime is criminal and he want to present his understanding to Britain, to west in general and no one is able to stop him," Berezovsky says.
Asked if Litvinenko was working for him, Berezovsky says, "Yeah, initially he worked just for me."
Berezovsky, one of the ultra-rich and powerful Russians known as oligarchs, knew what it was to have enemies in Russia. In 1994, a car bombing in Moscow nearly killed him and decapitated his driver. This was followed by other attempts.
Once, Berezovsky says, Litvinenko, the loyal intelligence operative, was ordered to kill him. "He got an order to kill me and he came to me and informed me about it," he recalls.
Berezovsky fled to London in 2001, and set up housekeeping in a heavily guarded estate near Windsor castle. By his own estimate, he has spent more than $100 million to attack the Russian government, its intelligence agency, and President Putin himself.
"Do you think that Litvinenko's relation to you further endangered his life?," Simon asks.
Yes. Unfortunately, I should say yes," Berezovsky acknowledges.
And Berezovsky says Litvinenko saved his life once again in London. If Litvinenko hadn't been targeted, Berezovsky is convinced, he would have been.
As long as Scotland Yard is continuing its investigation, Berezovsky told 60 Minutes he doesn't want to talk about who ordered the murder.
But this is what he said about the Russian intelligence agency and Putin.
"He's absolutely, absolutely bandit, from my point of view, yeah, and they, they, they decide to kill him," Berezovsky says.
Asked who is "they," Berezovsky tells Simon, "I don't want to create any problem for those who investigate this story. If you want, I might just use the, the English joke 'If it looks like duck and quack like duck, it means duck.' That's it, what I may tell you now."
Berezovsky told 60 Minutes something else as well: that he had recently reduced his financial support of Litvinenko.