A business tycoon who died after falling four storeys and getting impaled on spiked railings below owned millions to the Russian mafia and was once dangled out of a hotel window by gangsters, according to reports.

Scot Young, a bankrupt telecommunications mogul, was found dead outside his penthouse flat in Marylebone, central London on 8 December.

Police said they are not treating the 52-year-old's death as suspicious, but there have been calls from those close to Young for Scotland Yard to investigate the possibility he was murdered.

Young, who declared himself bankrupt in 2010 after losing his £400m ($650) fortune in a disastrous Moscow property venture, was jailed in 2013 for a "flagrant and deliberate" contempt of court after repeatedly failing to disclose what happened to his assets.

He also recently went through one of the most expensive divorces in UK history, eventually settling a fee of around £26m with his estranged wife Michelle.

A friend of Young has now said he once owned millions "to the wrong sort of people" and was hung out of a hotel room window in London because of unpaid debts.

The man, who wished to remain anonymous, told the Telegraph: "I do not believe for one minute Scot committed suicide, my heart tells me he was killed. There is no way he would have jumped to his death.

"I knew him very, very well, we have been friends for over 20 years. We are all very scared about what might happen. I believe Scot was murdered."

He added: "Two years ago he was hung off the balcony of a hotel room at the Dorchester by Russian mafia he owed money to, before he went to prison. He never went back there after that. He owed a lot of money to the wrong sort of people."

A Met Police spokesperson said: "Police were called to Montagu Square, W1 at 17:18hrs on Monday, 8 December to reports of a man having fallen from a fourth floor window.

"A man, believed aged in his early 50's, was pronounced dead at the scene. The death is not being treated as suspicious at this time."