What do the Arabs want in Iran? The question has long puzzled me. They want to see the back of the Islamic revolutionary regime (most people do), but their relations with its pro-Western, nationalist predecessor were hardly very good either. Several years ago, over dinner in Istanbul with a group of veteran Saudi diplomats, I thought I glimpsed an answer. One began, in a typically oracular manner, talking of a journey he had taken along the southern coast of Iran as a student in the 1960s. He asked the rest of us what language we thought the people there had uniformly spoken (the answer: ‘Arabic’). And he then went on to evoke a historical version of the Persian Gulf that had existed until less than a century before: of a peaceful, undivided, tight-knit Arabian community, the whole coastline ringed by Arab emirates and sheikhdoms.