The government should go even further and require all property-owning companies to disclose who really owns them, said Nick Maxwell, head of research at Transparency International. The advocacy group will publish a report on how British real estate is used by money launderers this week.Secrecy Preference

The amount raised from the levy on luxury homes shows there’s a “big preference for secrecy,” he said. “It’s part of the problem of offshore ownership in the U.K.”

Buyers of luxury real estate often purchase the holding company rather than the property directly to avoid paying stamp duty, a tax owed when a sale goes through. This means the name of the owner on paper doesn’t change, while the real proprietor does, according to the Serious Fraud Office’s proceeds of crime unit.

Former BTA Bank chairman Mukhtar Ablyazov arrives under police protection at the courthouse in Lyon, on Oct. 17. He’s now in jail in Lyon, France, awaiting a verdict on his appeal against extradition to face criminal charges in Russia or the Ukraine in the embezzlement case.

Photographer: Philippe Merle/AFP via Getty Images

More than 12,500 London properties worth over 48.5 billion pounds were sold by offshore companies from 2012 through 2014, Land Registry data compiled for Bloomberg News show. The registry only has information on sales, not purchases.

More than a third of the sellers were out of the British Virgin Islands, where Mount Properties Ltd., which bought Carlton House, is based. Mount Properties is owned by Mega Property Ltd., a company based in the Marshall Islands, according to the High Court ruling on seizing Ablyazov’s assets including the home. Neither jurisdiction requires disclosure of beneficial owners of companies.Marble Hallway

The home on The Bishops Avenue, one of two London streets known as Billionaires Row because of the large number of wealthy residents, has a manned security hut and security cameras out front. Inside, a marble hallway with a wrought-iron staircase welcomes visitors, according to broker Glentree Estates, which is acting on behalf of receiver KPMG LLP.

The High Court found Ablyazov in contempt for lying about owning the home and other assets. After he didn’t show up for his sentencing hearing -- he got 22 months in prison -- it was discovered that he’d fled the U.K. He’s now in jail in France, awaiting a verdict on his appeal against extradition to face criminal charges in Russia or the Ukraine in the embezzlement case. BTA, once Kazakhstan’s biggest bank, was bought last year by Kazkommertsbank and a local businessman after defaulting twice.Fraud Victim

Ablyazov “is the victim of a massive fraud committed against him by a dictatorial regime,” according to a statement from his lawyer, Peter Sahas.