Leonid Rozhetskin's model wife is now fearing for her life and is receiving round-the-clock protection.
But despite hiring a team of £1,000-a-day bodyguards to protect her London home, last week the MoS was able to walk right past them and up to her front door.
Natalya Belova is holed up in the couple's £3million London penthouse with their three-year-old son.
She has told friends she fears she will be next to "vanish" and has hired a team of bodyguards from Kroll Associates, the close-protection agency of choice among wealthy Russians who have to deal with kidnapping and extortion threats.
Roman Abramovich, the billionaire owner of Chelsea FC, paid the agency millions to protect him before poaching their head of security to work exclusively for him.
Last week a team of at least five well-built bodyguards surrounded Natalya's home.
But as two guards stood on the pavement looking directly up at the apartment, a Mail on Sunday reporter and photographer strode up unchallenged to the front door.
With the bodyguards standing just a few yards away, our reporter buzzed the outside intercom to Mrs Rozhetskin's flat ? and she simply buzzed them inside.
The reporter and photographer then got into the lift and travelled up to her floor.
There was no guard outside the flat and Natalya could clearly be heard talking to her son inside.
Our man rang the bell outside the door but Natalya did not come to the door. It was only after he rang the bell again that several people came sprinting up the carpeted stairs.
Two security guards rushed into the corridor. One, dressed in a suit and at least 6ft 5in tall, said: "I am afraid I am going to ask you gentlemen to leave."
The guards then shepherded the reporter and photographer down the stairs, alerting more colleagues at the bottom that they were coming down.
Outside, one of the protection team came over to speak to them.
He apologised in case his colleagues may have appeared impolite, acknowledged that Natalya was inside and asked if the newspaper would be identifying the address. The reporter said the newspaper would not.
A source close to Natalya has said she fears her husband has been murdered.
"Forget all the rubbish that has been written about this being a hoax, or that Leonid is doing this for publicity," said the friend.
"Natalya believes that he has been murdered for speaking out against the same pollutants who killed Litvinenko."