The question of whether a war will break out over Iran’s nuclear programme has been around for so long that is easy to become almost blasé. In 2006 Benjamin Netanyahu, the Israeli prime minister, was already asserting dramatically: “It’s 1938 and Iran is Germany.”

This year, however, feels different. The threat of war is much more real. A conflict would begin with an Israeli bombing raid on Iran. But it would be likely swiftly to draw in the US – probably the UK and France, as well, and possibly the Gulf states and Saudi Arabia.

Israeli fears are driving the process. Ehud Barak, the Israeli defence minister, has talked of Iran entering a “zone of immunity” – in which its nuclear programme becomes unstoppable – in the coming months. The Israelis are particularly concerned about plans to put Iran’s uranium-enrichment facilities into hardened underground bunkers. Leon Panetta, the US defence secretary, is said to believe there is a strong possibility of an Israeli attack in April, May or June.