Whatever happened to America’s desert kingdom? In the four months since Salman bin Abdulaziz al Saud became king of Saudi Arabia, everything we thought we knew about this supposedly risk-averse US ally has been turned on its head.

In a ruling house long known for geriatric leadership, the new king has pushed aside elder statesmen and seasoned technocrats alike in favour of an impetuous and uncredentialled son, Mohammed bin Salman, who may be in his late twenties.