THE CROWD began gathering at 6am last Saturday outside the Qwest Centre arena in Omaha, Nebraska. Billboards advertised gigs by U2 and Paul McCartney. Motley Crue had just played Qwest, accompanied by leashed dwarves and PVC-clad trapeze artistes. This crowd was more soberly attired. Shivering on an unseasonably cold morning, they were here to see Warren Buffett, the world’s most successful investor. But he, too, would sing.

After the 17,000 Buffett fans had taken their seats, giant video screens came to life above a small stage. Buffett appeared wearing dungarees, a wooden shack in the background. “Somewhere over the rainbow. Way up high. There’s a land that I heard of. Once in a lullaby...” Buffett loves to sing. He does it every year, sometimes accompanying himself on a ukulele.

Before he can get to the song’s tricky bit a tornado destroys the house and whisks Buffett off to Oz on a cartoon adventure, accompanied by his caustic sidekick Charlie Munger as the Tin Man and friends Bill Gates, Microsoft’s co-founder, as the Scarecrow and Arnold Schwarzenegger as the cowardly Lion.

It’s the start of the Berkshire Hathaway annual shareholder meeting. It is a strange amalgam of shopping trip, county fair, weekend MBA, history lecture and social club. The meeting always starts with a film, made by Buffett’s daughter, Susie.

Shareholders give the film rapturous applause, but there is trouble in Oz. Buffett is now 74, Munger 81. Both have sharper minds than most men half their age but neither is immortal. Buffett’s wife, Susie, died this year and mortality and succession seem to be much on his mind.

Like many conglomerates, Berkshire is a bizarre collection of businesses. Among other assets, it owns 8% of Coca-Cola, 12.1% of American Express, 18.1% of The Washington Post, Fruit of the Loom leisurewear, Acme building products and the insurers General Re and Geico.

What these investments have in common is Buffett. For the long-term investor there have been few opportunities as rich as Berkshire. Since 1965, its Class A stock has returned an average of 26% a year. It now sells for $84,950 (£44,767) a share, valuing Buffett’s 29% stake at $42 billion.

Buffett has become a hero to the wider business community. Valuing his integrity above all, he has survived the wave of corporate scandals unscathed. Malpractice in the insurance industry has led to regulators in Australia and America probing his companies, and late on Friday Berkshire disclosed that the Securities and Exchange Commission planned to file a fraud complaint against an unnamed executive at General Re, one of its largest insurance businesses. But not even Eliot Spitzer, New York ’s crusading attorney- general, believes Buffett has sinned. He is almost untouchable — the patron saint of American capitalism.

Buffett invited Gates on to Berkshire’s board this year. He described Gates, the only man who is richer than him, as “a trustee of the will”, who can ensure the company is run as Buffett would want it to be.

But not even Gates and Buffett’s combined wealth and brainpower can halt Buffett’s slide to the high-risk end of the actuarial tables. Investors are worrying about the future. Fitch, a credit-rating agency, recently downgraded its outlook on Berkshire from “stable” to “negative”, noting in its report that Fitch “does not believe Mr Buffett’s talents can be easily replaced, or that Berkshire’s strategies would be sustainable in his absence”.

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BUFFETT and Munger are quite a double act. The two have worked together since the 1960s. Buffett is chatty, cordial, a joker. Munger is patrician and severe — Buffett calls him “the abominable no man”. Buffett is a liberal Democrat, Munger a right-wing Republican. They adore each other — rarely does one miss an opportunity to praise the other.

Asked about his best investment, Buffett named Munger, adding “he works cheap, too”.

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