Newshounds love the $90bn “merger” of mining behemoth Xstrata with commodity trading giant Glencore. At last, after months of bad news, a gigantic deal seems to signal the return of capital. Big fees, big companies, big egos: you could almost be forgiven for thinking life has returned to normal.

But in the euphoria that inevitably surrounds mega-deals, it's easy to forget that most mergers fail; that is, they do not accomplish the strategic goals for which they were designed in the first place.