When Warren Buffett so much as scratches his nose, the investment world sits up and takes notice. So the Buffettologists will be all over the latest acquisition by the world’s smartest investor.

While his rivals were still digesting their sprouts, Mr Buffett announced on the evening of Christmas Day that Berkshire Hathaway was paying $4.5 billion (£2.25 billion) for majority control of Marmon Holdings, an industrial conglomerate owned by the Pritzker family of Chicago.

Outside his insurance company investments, this is Mr Buffett’s biggest deal yet. Given Berkshire’s investment preferences, there were few surprises in the deal. Marmon’s products are easy to understand and low-tech. It makes stuff such as railway tankers, plumbing materials and household wiring. The company is nicely unfashionable - a sprawling conglomerate of 125 subsidiaries. And it looks cheap. Details are scant but Mr Buffett appears to be paying less than ten times after-tax profits and less than one times sales.

All very Buffett. However, the timing of the deal and the geographic market of Marmon - overwhelmingly the US – make it more interesting. Berkshire is no stranger to overseas investments yet chose to snap up an asset in its own backyard just as America is threatened with a severe downturn, possibly a recession.

Of course, Berkshire is a famously long-term investor and isn’t particularly bothered about getting its timing exactly right. Nevertheless, this is a vote of long-term confidence in the US economy generally and in the poleaxed housebuilding sector in particular.

The other intriguing aspect is what Mr Buffett has chosen not to invest in. It’s a certainty that the investment banks seeking out rescue capital over the past few weeks would have had Omaha, Mr Buffett’s home town, high on their list of places to visit. Mr Buffett has the cash ($50 billion and rising), the reputation and the appetite to do just these kinds of big, difficult deals – ballsy investments conventional funds would shun. “I can spend money faster than Imelda Marcos when things are right,” he once said.

Rumours he was poised to invest in the troubled investment bank Bear Stearns, then in the mortgage lender Countrywide Financial, turned out to be false. Since then Citigroup, Morgan Stanley, UBS and Merrill Lynch have all gone out in search of rescue capital and have all struck deals with Middle Eastern or Asian sovereign wealth funds.

In every case, Mr Buffett has been nowhere to be seen.

The idea that Mr Buffett wants nothing to do with banks doesn’t square with the facts. He was certainly bruised by his investment in Salomon Brothers in the 1990s. He joked at the time: “I felt like the drama critic who wrote ‘I would have enjoyed the play except that I had an unfortunate seat. It faced the stage’.” But in the end he exited Salomon with a respectable profit when it was offloaded to Travelers, later merged with Citigroup. Bank investments like American Express and Wells Fargo have also paid off handsomely.

In the latest deals, the banks were dangling seemingly enticing terms. Citigroup offered a juicy 13 per cent coupon on the convertible shares sold to Abu Dhabi while Merrill gave the Singaporeans a 12 per cent discount and a money-back guarantee. Yet Mr Buffett appears not to have been swayed.

Goldman Sachs reckons Wall Street’s finest are due to confess to yet another wave of sub-prime writedowns. Mr Buffett’s apparent indifference thus far to any of the approaches and blandishments from said banks suggests he might agree.

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