The hedge fund manager Chris Hohn, who runs The Children's Investment Fund (TCI), has donated £466 million to the foundation run by his wife, Jamie Cooper-Hohn, that benefits projects across Africa and the developing world.
The donation dwarfs other recent gifts. Sir Tom Hunter, the Scottish billionaire, has promised to give £1 billion to charity, but that was spread over his life time. David and Heather Stevens, the founders of the insurance company Admiral, gave away £100 million.
The Hohns have given almost £800 million in only four years, making them Britain's most generous philanthropists.
Mr Hohn, 41, who has a reputation for being aggressive and ruthless with the management of the companies he invests in, set up TCI in 2003. The fund was structured so that a percentage of the earnings go directly to its charitable arm, the Children's Investment Fund Foundation (CIFF).
The couple are considered pioneers among the "new philanthropists", the super-rich who are not only giving away a large proportion of their wealth but increasingly controlling the charities too.
As president of CIFF, American-born Mrs Cooper-Hohn, 43, meticulously researches each cause to find those that will produce "transformational change" on a large scale.
She says she runs the charity using the business model of her husband's fund. She once said: "I was very eager that if we did this we would do it very much in the way Chris invests, making long-term, well-researched investments, bringing business rigour and a private-sector approach into development."
The foundation has given money to the Clinton Foundation for the treatment of HIV/Aids; to a scheme to help orphans in Malawi; and to emergency aid projects in places such as Darfur.
After the charity gave £2.9 million to HIV and Aids work conducted by Bill Clinton's foundation, the former president said that the Hohns' "marriage of business and philanthropy provides a great tool to effect serious change in the developing world".
Originally the Hohns planned to give £5 million a year to CIFF but, because of the success of TCI, donations soared each year. In 2005, the foundation gave £500 million.
Last year the cash injection leapt to £235.8 million. CIFF is now thought to be Britain's fastest growing foundation. The Hohns, who avoid publicity and about whom little is known, have four children and live in north London. Mrs Cooper-Hohn has given an exclusive interview to tomorrow's Sunday Telegraph.
In it she said: "One of the things that attracted Chris and I was the shared sense of something that is larger than ourselves and the thrill that we can have a positive impact.
"We work well together – he is passionate about helping, I'm more pragmatic about it. The aim is that Chris's money will result in long lasting and radical change."
Mr Hohn's father, a mechanic, came to Britain in the 1960s from Jamaica. He married Winifred, a secretary, and lived in Sussex. His son went to Southampton University then Harvard Business School. There he met Mrs Cooper-Hohn, who was brought up in Chicago.
TCI manages more than £5 billion for clients and made returns of more than 40 per cent on investors' money in 2006 and of 50 per cent in 2005. Mrs Cooper-Hohn does not take a salary.
Britain's richest people are involved in unprecedented levels of charitable giving. It is estimated that the top 30 philanthropists among Britain's richest 1,000 people either gave away or pledged to give away £2.38 billion over the year to May 2008.
Sir Tom Hunter, the Scottish entrepreneur, has pledged to give away £1 billion in his lifetime through his Hunter Foundation.
Meanwhile Peter Cruddas, the founder of the internet securities dealer CMC, has set up the Peter Cruddas Foundation to handle his donations. He has endowed the fund with £100 million. Margie Moffat, the co-founder of the AT Mays travel agency, has put £50 million into a charitable trust for Scottish causes.
Eric Clapton raises funds for the Crossroads Centre on Antigua, which he founded to help alcoholics and recovering drug addicts.
Up to 30 per cent of Elton John's earnings from live performances go to charity.
Sir Tom Hunter, The Hunter Foundation - £1,013.8m
Lord Sainsbury, Sainsbury family charitable trusts - £233.6m
Peter Cruddas, The Peter Cruddas Foundation - £100m
Anthony d’Offay, Gift of art collection to the Tate and National Galleries of Scotland - £97m
Margie and Jamie Moffat, The Moffat Charitable Trust - £54.8m
Johan Eliasch, Amazon rainforest - £50m
Sir Ian Wood, The Wood Family Trust - £50m
Sir Elton John, Elton John Aids Foundations £25.8m
Michael Spencer, One day’s revenue at Icap to good causes - £9.2m
Hermann Hauser, Centre for Entrepreneurship, University of Cambridge - £8m