George Soros, the billionaire best known for breaking the Bank of England, is returning money to outside investors in his $25.5 billion (Dh93.63 billion) firm, ending a career as hedge-fund manager that spanned more than four decades. Soros, who turns 81 next month, will hand back the money, less than $1 billion, by the end of the year, according to two people briefed on the matter. His firm will focus on managing assets solely for Soros and his family, according to a letter to investors. Keith Anderson, 51, chief investment officer since February 2008, is leaving, said the letter, signed by Soros\'s sons Jonathan and Robert, who are co-deputy chairmen. \"We wish to express our gratitude to those who chose to invest their capital with Soros Fund Management LLC over the last nearly 40 years,\" they said in the letter. \"We trust that you have felt well rewarded for your decision over time.\" Article continues below The move completes Soros\'s transformation from a speculator, who in 1992 made $1 billion betting that the Bank of England would be forced to devalue the pound, to philanthropist statesman, a role he first imagined for himself as a Hungarian immigrant studying at the London School of Economics after the Second World War, according to Soros\'s writings. In the last 30 years, he\'s given away more than $8 billion to promote democracy, foster free speech, improve education and fight poverty around the world, he said in a recent essay. Family assets Soros\'s sons said they took the decision because new financial regulations would have made it necessary for the firm to register with the Securities and Exchange Commission by March 2012 if it continued to manage money for outsiders. Because the firm has overseen mostly family assets since 2000, when outside money accounted for about $4 billion, they decided it made more sense to run it as a family office, according to the letter. The rule calls for hedge funds with more than $150 million in assets to report information about their investors and employees, the assets they manage, potential conflicts of interest and their activities outside of fund advising. Registered funds will also be subject to periodic inspections by the SEC. \"We have relied until now on other exemptions from registration which allowed outside shareholders whose interests aligned with those of the family investors to remain invested in Quantum,\" the executives said in the letter, referring to its flagship Quantum Endowment Fund. \"As those other exemptions are no longer available under the new regulations, Soros Fund Management will now complete the transition to a family office that it began eleven years ago.\" Soros, who controls more than $24.5 billion for himself, his family and his foundations, declined to comment on the letter. Last year, Stanley Druckenmiller, Soros\'s chief strategist from late 1988 until 2000, closed his money-management firm, Duquesne Capital Management LLC, and created his own family office. While Quantum has returned about 20 per cent a year, on average, since 1969, when its predecessor was started, according to a person familiar with the firm, the fund\'s performance has suffered in the last 18 months. In the first half of this year, Quantum lost about 6 per cent, the person said, following a gain of 2.5 per cent in 2010. Other macro funds have returned 5.6 per cent in the last year-and-a-half, according to Chicago-based Hedge Fund Research Inc.