If Jamie Dimon was pondering a career change as a fortune-teller, he’d be wise to stick to the day job. On the other hand, if someone of Dimon’s stature could be so wrong about the banking turmoil that continues to sweep across the US, a cynic might ask whether he was still the right person to be running one of the world’s largest financial institutions, particularly when that organisation is right at the centre of Government-led efforts to prop up the whole system.