Matthew Ames, son of troubled overseas property company Harlequin's chairman David Ames, has been found guilty of two counts of defrauding investors.
The verdict was reached today by a jury at Isleworth Crown Court.
Ames - who last August was "monitoring things" for his father at Harlequin's flagship Caribbean resort Buccament Bay - was charged with fraud in December 2012 in relation to his two green investment firms, Forestry for Life and the Investor Club.
Harlequin said in January that Matthew Ames is no longer overseeing Buccament Bay.
Forestry for Life and the Investor Club took around £1.6m from investors who were promised 15% returns from teak tree plantations and rainforest protection projects.
However at the time the fraud was discovered by the City of London Police and the then regulator the Financial Services Authority (FSA), the two companies had just £310 between them.
During Ames' trial the court heard that instead of investing the money as promised, he used it to fund a lavish lifestyle of fast cars and luxury Caribbean accommodation.
Prosecutor Stuart Biggs accused Ames of running a "Ponzi scheme".
He said: "The method was to create an enticing glossy brochure. It included quotes from Prince Charles, Tony Blair and referenced the Kyoto Protocol and Harvard University. There was an added bonus you were doing something ethical.
"In truth no investments were made by either company, not a single piece of land was purchased abroad or a tree planted, or money kept safe in a separate account. It was used to pay company expenses, staff, and to support Mr Ames and his lifestyle."
City of London investigators found evidence £250,000 was paid out to investors, but it came from other clients' deposits and not generated by any investment.
By late 2010 interest payments to clients stopped and both firms were liquidated in March 2011 after the FSA became aware of the unregulated investments.
Ames was arrested in September that year and denied two counts of fraudulent trading between 2008 and 2011. He was disqualified from being a company director for 13 years by the Insolvency Service in August.
He will be sentenced on 14 March.
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