Russian buyers spent about £180m in the London housing market in 2013, according to estimates from Savills. Many agents expect this year's figure to be sharply higher, as the current wave of prospective buyers finalise their purchases.
Roarie Scarisbrick, director of the buying agent Property Vision, said: "A lot of the Russian clients we have been talking to over the last couple of years, who had just been considering buying here, have stepped up their plans and are getting on with it."
Mr Challis said the Treasury had been "surprised by the number of property holders that have retained ownership structures through a corporate vehicle".
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Despite a recent tax crackdown by George Osborne, the chancellor, many eastern Europeans still buy their London homes through a company structure to preserve their anonymity, according to tax advisers and housing market agents.
This use of offshore companies makes property assets harder for any international financial sanctions regime to target.
Charles McDowell, a property finder for wealthy buyers, said buying through a company structure was popular because "should there be any freezing of assets or something similar, they are as protected as they can be".
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"We have certainly seen an upturn in Russian buyers as well as eastern Europeans generally," he said. "Russians in particular are nervous about how any escalation in sanctions might affect them."
Michael Morris, a partner in Channel Islands law firm Collas Crill who advises rich international home buyers, said they purchase through a company because "the Land Registry is a public register and if you are extremely wealthy you may not want people to know where your home is".
David Cameron wants to remove the "cloak of secrecy" hiding corruption and tax evasion, and the government has just announced details of a new public register of beneficial interests.
The rules aim to force UK companies to reveal the names of their owners, but experts are doubtful that they will be effective.
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Gavin Hayman, director of campaigns at Global Witness, an anti-corruption group, said the government's new register would "help a bit" with targeting sanctions but would not be the complete solution because ownership could still be obscured using offshore companies. He said it would be worth exploring the case for requiring the Land Registry to list the beneficial ownership of property.
Bill Dodwell, of Deloitte, the professional services group, said: "The general sense is that if complete privacy is important you wouldn't be using a UK company in the first place."
Many property-owning companies are based in tax havens, although these have a relatively good record for collecting information on corporate ownership. But nearly 2m companies are formed each year in the US, almost always without obtaining the names of the people who will control them.
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Property agents are required to perform additional anti-money laundering checks on "politically-exposed" people, including those with close links to foreign governments, although the authorities have long been concerned about the difficulty of identifying potentially suspect real estate transactions.
George Osborne launched an initial crackdown on homes owned through companies in 2012, introducing a tax on dwellings held in a corporate envelope. It has been highly successful, raising five times the sum the government expected. Mr Osborne further tightened the tax rules on properties owned through companies in this year's Budget.
Richard White, head of UK real estate at advisory firm KPMG, said: "The tax law changes are based on an assumption that such structures are solely there for tax avoidance purposes.
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"However, there can be other, non-tax related reasons for high-profile individuals acquiring their private property through companies, such as the desire to preserve anonymity. This can often be as a result of the political sentiment in their country of origin, which we frequently see with Russian and eastern European investors."
Russians and eastern Europeans are particularly keen on buying large family homes on the Bishops Avenue in Highgate, north London, which is popularly known as "billionaires' row".
Jeremy Gee, a director of estate agent Glentree, specialises in selling homes in the area and is currently house-hunting for two "very serious buyers" arriving in London from Ukraine and looking to settle their families here quickly.
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Most Russian and Ukrainian owners of London homes hold them through companies in order to keep their identities private, Mr Gee said.