Barclays bank chief makes £15 million by selling his house

Bob Diamond, Barclays Bank's investment banking chief, bought the property in Kensington with his wife Jennifer for £10.5 million three years ago. It is now said to be under offer at £25 million.

Mr Diamond, 57, one of the City's highest- paid bosses, has been appointed by Mr Johnson to help set up and run his Mayor's Fund, which aims to raise money from business to help young people in underprivileged areas.

When he announced the appointment in April, the Mayor said he was delighted Mr Diamond had agreed to take on the role as he was "an extremely wealthy man and I know how much money they make at Barclays because they rip me off with their charges the whole time".

Even before his property windfall, the American-born banker was a controversial figure because of the scale of his £36 million pay, bonus and share package last year at a time when Barclays was being forced to write off £1.6 billion in bad debts.

At the bank's annual meeting last month, one shareholder said Barclays had gone "berserk" because it was paying Mr Diamond 24 times as much as Bank of England governor Mervyn King.

Mr Diamond's home is an imposing seven-bedroomneo-Georgian townhouse in Wycombe Square, a development built by St James, part of the Berkeley Homes group.

It stands on the site of the former Campden Hill tennis club and backs on to Holland Park School.

The identity of the buyer is a secret, but it has been reported that JK Rowling was looking to buy a second property in Kensington last year.

The multi-millionaire Harry Potter author was said to be interested in buying a home on a new, high-security gated estate.

The Wycombe Square development caused high-profile objections. It was refused planning permission by Kensington and Chelsea council but approved on appeal by John Prescott when he was deputy prime minister.

Mr Diamond's house has 8,000 square feet of space, with an indoor swimming pool, a gym and an underground garage for seven cars.

The former bond trader from Massachusetts joined Barclays in 1996 and has been credited with turning its investment banking arm Barclays Capital into one of the world's leading financial powerhouses.

However, his golden-boy image has been tarnished by the scale of Barclays' blighted investments in the American sub-prime mortgage market.

Mr Diamond, a staunch Republican who used to be a lecturer, is a sports fanatic with particular interest in baseball, football and golf - he has a handicap of eight.

In 2005, he presented Chelsea captain John Terry with the Barclays Premiership trophy.

He is also chairman of Old Vic Productions, the company behind Billy Elliot the Musical.

Mr Diamond, a father of three, has taken British citizenship but still describes himself as "very, very American".