Warren Buffett, the world’s second-richest man, saw third-quarter profits triple at Berkshire Hathaway, his investment vehicle.

The conglomerate benefited from gains in its vast stock portfolio to report profit of $3.24 billion (£1.9 billion), or $2,087 per Class A equivalent share in the quarter ending September 30. This was triple the $1.06 billion, or $682 per Class A equivalent share, reported a year earlier.

Berkshire’s insurance companies performed well, thanks to a quiet hurricane season. But its other operating companies struggled. Operating profits, were $2.06 billion, or $1,325 per Class A equivalent share, slightly lower than last year’s figure, but ahead of analysts’ expectations.

Revenue rose 7 per cent to $29.9 billion.

Berkshire owns more than 60 subsidiaries and it has major investments in such companies as American Express, Goldman Sachs, Wells Fargo and The Coca-Cola Company, which have experienced a wave of gains in their stock price since the second quarter of this year.

These gains helped boost Berkshire's book value to $126.07 billion, or $81,247 per share, up 10 per cent from three months earlier and 15 per cent from year end.

Most of the volatility in the company’s earnings is related to unrealised gains in the value of its derivatives. In the third quarter it reported derivative gains of $1.18 billion, against losses of $1.01 billion for the same period last year.

Mr Buffet has repeatedly expressed concerns about the shape of the economy this year, but in the last two weeks he has suggested that the low point has passed. Earlier this week he described his $34 billion investment in Burlington Northern Santa Fe, the American rail freight group, as a bet on the improving US economy.

Berkshire Hathaway said on Friday that it would fund half of the deal with internally generated cash and half with borrowings to be repaid over three years.

Fitch, Standard & Poors and Best, the credit ratings agencies, have since placed Berkshire Hathaway’s ratings under review, amid fears that the deal could expose his company to weaknesses in the economy at the expense of Mr Buffett’s more durable investments.

On Friday a New Orleans pension fund confirmed it was suing Berkshire Hathaway and Burlington Northern Santa Fe over the deal, arguing that Burlington directors breached their fiduciary duties “by attempting to coerce” shareholders into agreeing to the sale.

But Mr Buffett’s attention now is likely to be focused on Kraft, the US food group, which is poised to make a takeover bid for Cadbury, the British chocolate group.

Berkshire Hathaway is Kraft’s largest investor.

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