Thomas Cromwell: the triumph and tragedy of Henry VIII's right-hand man

In the spring of 1540 Thomas Cromwell was at the height of his power, but just a few months later he found himself at the scaffold on Tower Hill preparing to be executed for treason and heresy. What had gone so badly wrong for Henry VIII's right-hand man? As the BBC drama Wolf Hall returns for a second series, Rob Attar speaks to Cromwell biographer Diarmaid MacCulloch about the precipitous downfall of a man who seemed to have it all.