THE death of Susan Buffett, Warren Buffett's wife, last week brings to a close the life of probably the most influential force behind the world's most successful investor.

She was a director of Berkshire Hathaway, her husband's holding company, and president of the Buffett Foundation, which has contributed millions of dollars to educational groups, medical research, population-control groups and other charities.

Although the couple separated almost three decades ago, her husband had intended to pass on much of his $41 billion (£22.5 billion) fortune to her and they remained close. Buffett's three children have been given Berkshire stock over the years, but the billionaire has said that they must find their own way in the world.

Far from spoilt, the Buffetts have been forced to appreciate the value of money. Once when his daughter, Susie, needed $20 to get her car out of the airport car park, Buffett made her write him a cheque.

Susan Buffett was more outgoing and social than her husband, and after their children had grown up, according to biographer Roger Lowenstein, the two drifted apart. "All Warren needs to be happy is a book and a 60-watt bulb," she reportedly told a friend.

Encouraged by the songwriter and musician Neil Sedaka to embark on a singing career, she left her husband in 1977 and moved to San Francisco. But her singing did not really take off. The Buffetts never divorced and Susan Buffett even introduced her husband to his long-time companion, Astrid Menks, a Latvian-born waitress who worked in his home town of Omaha, Nebraska.

Susan Buffett's inheritance will probably go toward creating a charitable foundation that would be even wealthier than the Gates Foundation, until now the largest in the world.

Buffett, the world's second-richest man after Microsoft's Bill Gates, was with his wife when she died. Susan Buffett, who was 72, held about $3 billion in Berkshire stock — about 2% of the company whose class A shares now trade for more than $87,000 each. Her death may well remind investors that the 73-year-old founder is mortal, too. What happens to Berkshire Hathaway in his absence is certain to be one of Wall Street's great dramas.

Starting in 1956, Buffett built a fortune investing in brand-name companies that he understands, most famously Coca-Cola. His approach is simple, quaint even, and has attracted an army of followers. He pays no heed to macroeconomic trends or Wall Street fashions, looking for companies he believes to be undervalued and to have high growth potential and strong market share. Often as not he is right, and then waits for the rest of the world to catch up.
Buffett has said that in the event of his death, his 49- year-old son, Howard, would become chairman of the company. Howard Buffett is already a director of Berkshire Hathaway, but he will not be filling his father's shoes. Buffett has said he sees his son's role not in managing the business, but as a guardian of the Berkshire style of doing business.

On his death the role of "the Sage of Omaha", as Buffett is nicknamed, would be divided into two parts, with one executive responsible for investments and another for managing its companies.

Although Buffett claims to have chosen a successor, neither the public nor his anointed one have been let in on the decision.

Whoever they are, they will have a lot to live up to.