Ivan Glasenberg and Mick Davis have not even reached the altar, yet investors are celebrating a marriage. They assume that trader-cum-miner Glencore’s proposed $88bn “merger of equals” with diversified miner Xstrata is a done deal. But even if Mr Glasenberg’s Glencore and Mr Davis’s Xstrata can agree terms, there are reasons to ask whether this is merely a marriage of convenience.

Would Mr Glasenberg be pursuing the deal if Glencore did not already own 34 per cent of Xstrata? Almost certainly not. Merging traders and miners has not been tried before on such a scale, though there is no harm in trying. Glencore trades 40-60 per cent of the global volume of many commodities and needs new revenue streams. The lure of Xstrata is understandable: its growth projects in copper alone will account for about a fifth of all probable global production growth in the next decade, Jefferies estimates.

Which raises the real difficulty. By opting for the devil he knows,