There are calls for a major probe into London's property market after a £147million empire including the world-famous 221 Baker Street was linked to a former secret police chief accused of murder and money-laundering.
Investigators say that the Government should force companies behind property deals to disclose who their owners are, amid fears that the world's most notorious criminals are using exclusive British addresses to hide their dirty money.
The calls come after anti-corruption campaigners claim that huge swathes of Baker Street are owned by an unknown figure linked to the dead Khazak diplomat Rakhat Aliyev.
One of the properties allegedly linked to the notorious businessman include 221 Baker Street, which is where super sleuth Sherlock Holmes would have lived if his fictional apartment of 221b existed.
Aliyev - known as “Sugar” because of his vast holdings in the global sugar trade - was being probed by several European governments over alleged money-laundering and corruption at the time of his death.
He was found hanged in his Austrian prison cell whilst awaiting trial over the murder of two bankers, whose bodies were found dumped in barrels back in his homeland.
Investigators from Global Witness now say they have uncovered evidence that companies formerly owned and directed by Aliyev are linked to the a mystery and unnamed figure who owns of some of London's most exclusive properties.
They claim that between 2008 and 2010 four different UK companies – all controlled by the same parent company in the British Virgin Islands (BVI) – bought properties worth £147m in central London.
The campaign group says that current and former directors of these four companies had previously worked closely with businessman Aliyev, who was exiled after falling out with Khazakhstan's president in 2007.
Secrecy laws in the small British overseas territory mean that it is impossible to determine who owns the offshore parent company outright.
Investigator Chido Dunn said: "Like other great world cities, London appears increasingly attractive to the wrong people for the wrong reasons.
"Even Holmes and Watson would have their work cut out investigating the suspect cash flooding into its property market, because the system is so riddled with loopholes.
"Our research show property is a big blind spot in the UK’s anti-corruption fight, and that has dire consequences. Some of the Gaddafi family’s stolen loot ended up in London – a famous example but far from a one-off.
"Unless we know who is behind these companies and where their money has come, the cash will keep pouring in.”
At least £122billion worth of property in England and Wales is now owned by companies registered offshore.
In total, 75 per cent of properties whose owners are under investigation for corruption have used legal loopholes to keep their identities secret.
All four companies strongly denied the claims, stating that Aliyev was at no time either the ultimate beneficial owner or controlling party in any of them.
There is no suggestion that any of the companies or the individuals who manage them were involved in money laundering or any illegal activity.
However, Mr Dunn said: "This latest example shows the urgent need for transparency in the UK’s property market and its system of company ownership.
"All the signs for who owns this property empire point to someone close to Rakhat Aliyev and the Kazakh ‘ruling family’, but the real owner remains a mystery.
"We need to be able to know who owns London’s properties and where the money to buy them came from.”
The revelations come after top estate agents in London were caught out offering to help foreign criminals launder money through Britain's most expensive properties.
An undercover investigation found experts from some of the capital's best known firms were prepared to seal the deal on multi-million pound mansions even after being told the money to pay for them was the proceeds of crime.
Estate agents are required by law to call in the authorities if they believe that money-laundering may be involved in a property sale.
However, journalists posing as a corrupt Russian politician and his girlfriend found many were willing to ignore where the money was coming from in order to complete the sale.
The reporters viewed five mansions in central London ranging from £3m pounds to £15m, telling the property agents quite openly that the cash for the purchase was being made illegally.