For a man who came into office promising to clasp Iran’s hand if only it unclenched its fist, Barack Obama must have felt rather punch-drunk by the end of last week.

Mr Obama has built his foreign policy around the idea of engagement. The latest news from Iran, which has come to symbolise that diplomatic drive, has been overwhelmingly grim. Yet while he has had to harden his rhetoric against Tehran, the president’s effort to reach out to US adversaries continues unabashed.