The reign of Bill Gates as the world's richest man has come to an end after an American investor took the title held by the Microsoft tycoon for 13 years.

Warren Buffett, 77, head of the Berkshire Hathaway corporation, has landed the top spot in Forbes' magazine 2008 list of World Billionaires.

Buffett, who made his first dollar by reselling bottles of cola at a profit aged just six, has amassed a personal fortune of $62billion (£31 billion).

He is considered to be the "greatest investor of all time" and has had interests in firms such as Coca-Cola, American Express and Gillette.

Gates, whose wealth is estimated at $58bn (£29bn), has slipped into third place on the list, after Mexican telecoms tycoon Carlos Slim Helu who is said to have a fortune of $60bn (£30bn) was named the world's second richest man.

According to Forbes magazine, Buffett and Gates are said to be great friends rather than competitive adversaries. In 2006, Buffett announced he had earmarked the majority of his Berkshire Hathaway shares for charity.

At the time, the gift was valued at $31bn (£16bn), the largest of its kind in history, with most of it going to the Gates Foundation, which carries out humanitarian work in Africa.

For the first time, there are more than 1000 billionaires on the Forbes list, rising from 946 in 2007 to 1125 this year.

Together, those on the 2008 super-rich list, two-thirds of whom describe their wealth as self-made, have a combined net worth of $4.4 trillion (£2.2trillion) - the same amount as the projected US government's healthcare bill in a decade's time.

The list also carries entries of 50 billionaires who are aged under 40, including 23-year-old Mark Zuckerberg, the founder of social networking site Facebook, who is valued at $1.5bn.

Billionaires listed in Forbes come from 54 countries and the top 10 includes four Indians who have made their fortunes through steel and real estate.

The average age of a billionaire on the Forbes list has dropped to 61, thanks in part to the growth of wealth in Russia, where the average age of a billionaire is 46.

There are 35 British billionaires, although 49 billionaires actually live in the UK and 36 of those call London their primary residence.