From Alexandria, he travelled west along the sea-coast with a small group of friends, following the whitened track to Paraetonium. At Paractonium, where Antony was one day to bid farewell to Cleopatra, he took his leave of Cyrene's envoys and set out southwards into the sand, his attendants mounted on camels with water for four days' journey. The sequel cannot be shared without a knowledge of its scenery and fortunately, Alexander's route has often been followed and described, the most telling account being that of Mr Bayle St John, if only because like Alexander he lost his way. In September 1847, having read his ancient texts with care, he equipped himself with camels, Bedouin guides and a moderate supply of water, and added the luxury of brandy and cigars; his notes are most helpful for what follows.

Soon after leaving Paraetonium, Alexander found himself in a wide expanse of sand, probably because his guides had led him too far west of the direct route which, as St John and others have remarked, should have run over hills of shale. His error was brought home unpleasantly, as a south wind sprang up and whipped across the desert, blinding the travellers in a sandstorm. For four days they wandered as best they could, exhausting their water and intensifying their thirst; supplies had almost run dry when clouds gathered and a sudden storm broke, 'not without the help of the gods,' so they believed, and this enabled them to refill their leather water-bottles.

On emerging from the sandstorm, they regained the long chain of hills which stretches inland from the sea, rising and falling in valley after valley until the reddish cliffs close in, streaks of white across their grotesque faces, and the final pass winds down a ravine to the sandy plains beyond. For the sake of coolness, Alexander would only move by night, steering by the clearness of the desert stars and trusting in the moon to light him on his way, as close as a man can come to his retreating ideal of silence, all quiet around him except for the faintest desert breeze. Even the ground came alive in the stillness, as the sides and floor of the pass were lined with dried-up shells which attracted the notice of the travellers and, according to St John, reflected the moonbeams till the whole road sparkled, like a mythical valley of Diamonds.

A gorge black as Erebus lies across the path [he writes], and on the right stands a huge pile of rocks, looking like the fortifications of some vast fabulous city such as Martin would choose to paint or Beckford to describe. There were yawning gateways flanked by bastions of tremendous altitude; there were towers and pyramids and crescents and domes and dizzy pinnacles and majestic crenellated heights, all invested wjth unearthly grandeur by the magic beams of the moon but exhibiting, in wide breaches and indescribable ruin, that they had been battered and undermined by the hurricane, the thunderbolt, the winter torrent and all the mighty artillery of time.

Amid this Gothic grandeur, Alexander once more lost his way.

According to Callisthenes, two crows came to his rescue, cawing to round up the stragglers and flying steadily in front until they had set Alexander back on the proper track. Ptolemy, never a man to be outdone, claimed in his history that two talking snakes had acted as guides not only to Siwah but also the whole way back again. These miracles must not be dismissed, though they are a warning that like Alexander, the truth of the Siwah visit was lost from the very start; the travellers did indeed notice many snakes on the way to the oracle, a fact which can be deduced from Theophrastus, pupil of Aristotle, who mentions their numbers in his book on botany, a work which drew its original information from members of Alexander's expedition. As for Callisthenes's crows, they have been sighted since; St John too went astray in the hills and while waiting for his Bedouin guides, he noticed two crows wheeling in the air away to the south-west. Had he followed them, he would have struck the very road he wanted, so it is perhaps no coincidence that the valley in question is still known to natives as the Pass of the Crow.

From the terrors of the pass, Alexander came down into a plain of sand, too hot for any vegetation, which stretches for some ten miles to the foot of the Milky Mountains. Here, among more cliffsides of the wildest architectural shapes, he followed the road out into the open, passing over a level basin of grey gravel. With a change so typical of the desert, on its far side the gravel falls abruptly into a plain of luxuriant palms, bounded by cliffs on either flank and walled across the middle by isolated rocks of massive shapes and sizes. In this, the oasis of Garah, lay the first cities of the people of Ammon; water, hospitality and shade were at last guaranteed and 'the vivid contrast of barrenness and fertility', writes St John, 'where life and death exert their sway beneath the infinite emblem of immortal serenity, excite mingled emotions of wonder and delight'.

From these preliminary cities of Ammon, one day's travelling was enough to bring Alexander to the second oasis, site of the Siwah oracle. Though rapid, his journey was no easier, for on leaving the palm-groves of Garah, he would have wound his way up yet another series of gorges, finding himself again on a gravel plateau, flayed by the heat. It is a place of no comforts until at its edge it too falls into one last ravine, only ten miles away from Siwah, first across valleys of whitened sand, then across land hardened and broken with lumps of natural salt, a rich deposit which the priests of Ammon would pack in baskets and send to the table of the Persian kings. The landscape dazzles the eye, as the salt-fields and dried up salt lakes have all the glare of snowbound glaciers. Before their whiteness can get the better of the traveller the oasis of Siwah has intervened, sweeping its greenness between the remaining pockets of sterility: palms and fruit-trees crowd round the streams, a home for quail and falcons, pomegranates and meadow-grasses, and for ram-headed Ammon, one of the four most truthful oracles known t« the Greek world.

The oasis is insulated by saltfields and marshes into a space some five miles long and three miles broad. Near its eastern edge, Alexander would come directly to his destination, the citadel now known as Aghurmi which protrudes on a cliff of limestone eighty feet above the plain. At the time of his visit, it was divided into three enclosures, the inner one for the palace of the rulers, the next for their family, their harem and the shrine of the god, the outer one for the guards and barracks. Beside the temple stood a sacred spring in which offerings to the god were purified; this is still visible, connected to the inner courts of the temple. About half a mile to the south-east stood a second shrine, also known to the Egyptians but less patronized by Greek pilgrims, though they knew of its fountain and wrongly believed it to be miraculous, thinking that it alternated between hot and cold at different times of the day. The Greeks, however, had no thermometers. Alexander's officers picked up its native name of Well of the Sun and linked it, characteristically, with their own Greek myth of Phaethon, fallen driver of the Sun's chariot.

Both for the visitors and the visited this sudden arrival was momentous. Alexander had been travelling for at least eight days through country of the most fantastic outlines, illusion and miracle around him at every mm. He was lucky to have survived, and his sense of relief on reaching the oasis is not difficult to imagine. The people of Siwah would have been no less excited. Historically, their oasis had long been a backwater, never visited by Pharaohs and sheltered from modem life by its surrounding desert; even in the twentieth century its local customs were still thriving, including homosexuality to the point of all-male marriage. A visit from a Macedonian conqueror would have stirred all the natives from their homes, and no doubt Alexander would have promptly made himself known to the ruling family who, like all Libyans, were identifiable by the single-feather headdress which they wore tied into their hair. Gossip claimed that Alexander also bribed Amnion's priests in order to be sure of receiving the answers he wanted, but any consultant of a Greek oracle would first pay the god honour, and it is unthinkable that Alexander gave advance warning of his questions and desired answers; his whole consultation depends on secrecy and ambiguity.