We need political leaders with real world experience. Too many of those who govern us have never worked outside politics. It is a frequent cry. But if we think business leaders are the answer, Donald Trump, the Republican presidential candidate, is providing a near-daily display of how hard it is to leap from running a business to winning elections.

There are two reasons. First, business leaders such as Meg Whitman and Carly Fiorina, who have both lost elections, did not seem to grasp that holders of political office have less control over events than does a chief executive. While a business boss can hire, fire, acquire and sell, even the US president is hemmed in by the constitution and can be stymied by Congress, as the political economist Francis Fukuyama has noted.

British prime ministers have more executive and legislative power but still have to accommodate rivals who might challenge for their job. The aggravation Tony Blair tolerated from his chancellor Gordon Brown? No chief executive would put up with it for a week, let alone 10 years.