I had barely caught up with Barry Cunliffe’s recent book on Brittany and the Bretons when news came of his latest foray into the archaeology and history of places on the edge, a marvellously rich book in which the Sahara holds centre stage but plenty is happening around the periphery. The problem, as he points out, is that the early history of northern Africa has been largely ignored by those writing about the Mediterranean, partly because of a supposed lack of data, although when he adds up what we do know it becomes obvious that the problem is often that people have been searching for the wrong sort of data. Excavations, travellers’ tales and, in particular, an awareness of the interconnectedness of the history of different parts of northern Africa have allowed him to open up a lost world. Note the broadness of the term ‘northern Africa’: Cunliffe looks far beyond the Maghreb, the Sahel (a word meaning ‘the shore’) and the northern edges of sub-Saharan Africa to include Nubia, Ethiopia and even the eastern flank of Africa, right down to Zanzibar.

At the heart of his account lie the sometimes sandy, sometimes rocky wastes of the Sahara. The title of his book plays on the common analogy between large deserts and maritime spaces. These deserts are areas in which it is important to keep on the move, never straying too far from the islands or oases where fresh water and food are available. A captive abandoned mid-Sahara without supplies had a not much greater chance of surviving than one of the slaves all too frequently thrown overboard from a transatlantic sailing ship. Yet deserts are subtly different from seas: as the seasons change, their boundaries move. Splashes of rain can bring the barren land to life, ‘like grass that grows fresh in the morning, and in the evening fades and dies’, to quote the Psalms. Nor has the Sahara always been dry. Prehistoric paintings reveal that it was at one time inhabited by a Noah’s Ark of wild animals, containing hippos as well as humans; it became a full desert only in the fourth millennium BC. The Sahara contains Lake Chad and there are watercourses, such as the Nile, along which vast quantities of grain can be grown, while the Niger river played a prominent role in the trade in gold across the Sahara.

Above all, the Sahara is a place that people have managed to cross. For Fernand Braudel, who lived for several years in Algiers, the Sahara was the counterpart of the Mediterranean and the Maghreb was a ridge not dividing these spaces but connecting the sea of water with