These women were from Thebes, of Jewish race, experts in the cultivation of the silkworm and the manufacture of robes and vestments for court occasions, who had been carried off from their homes and brought as a gift to the city of Palermo by the Admiral of the Fleet, the Emir of Emirs, George of Antioch, on a raid he had made into Greece two years before. Usually I gave Sara coin – it was what she preferred. But I handled money so much in my work that I liked sometimes to make her a present, some small trinket. Along with my clothes and the rent for my lodgings and the care of my horse, my visits to the Tiraz were a main part of my monthly expenditure.

The light was fading as I set out and the lamps at street corners were being lit. There was the smell of spilt water round the troughs of the pump near my house, a strangely strong odour, though made from nothing but slaked dust and hot stones; as always, it evoked some longing in me, though I did not know for what, or whether it was more than merely a feeling of loneliness.

This was the time of day when the street sweepers came into their own; sweepers they called themselves, but they were scavengers in fact. They were out now in force, sacks roped across their bodies. Of late months they had been coming to the attention of our Diwan. They were unruly; they were too successful. It was a closed company now, impossible to enter without a permit from one of the clan chiefs who controlled the various districts of the city, and had armed men at their bidding and skimmed off a portion of the sweepers' takings, as they did with beggars and whores. This was made more complicated by the fact that the dominant clans were of different races, Arabs in the Kalsa, Greeks on the south side, Sicilians in the area of the harbour. Disputes over territory arose from time to time and killings occurred. This was acceptable, so long as a proper balance was maintained. Lately, however, the balance had begun to tilt. There had been pitched battles between bands of sweepers, the number of deaths had increased very noticeably. ›From being a simple matter of bribes and intimidation, it had been dignified with the title of fiscal malpractice, and so it had come to the attention of the Diwan of Control. So far no remedy had been found. It was obvious that the sweeping, or scavenging, or whatever one called it, mainly took the form of theft; the people were poor, there were not pickings enough in the streets of Palermo to maintain more than a handful of lawful scavengers.

I fell to pondering the matter again as I walked along. The problem was threefold: how to stop the thefts, enlarge the King's coffers and have the streets swept clean. The sweepers could be made to wear a uniform of some kind, with a colour that would mark them out, yellow perhaps. Then people would be able to watch them more narrowly, especially when they were gathered in groups. Bolder, more likely to come to the notice of the King and gain his approval, would be to change their constitution altogether, form them into a single company with a new name, The Noble Company of Street Cleaners, wearing the royal emblem and regularly paying a fixed sum, or perhaps a portion of their earnings, into the Royal Treasury. In that case it would no longer be a bribe but a tax, and so quite lawful. But the difficulty here, apart from the hostility it would arouse among the chiefs, was that they had no earnings, properly speaking, only the proceeds of their thefts. Could people be persuaded to pay to have their streets cleaned? It seemed unlikely.

Perhaps this too could be imposed as a tax. Meanwhile the scavengers might be required to carry broom and shovel; thus encumbered they would find it less easy to steal, but on the other hand a shovel in the wrong hands could be a formidable weapon…

These fruitless thoughts occupied my mind until I came to the little square close to the Buscemi Gate where the goldsmith had his furnace. I watched him work for a little while, hammering out softened gold to thin leaf on his anvil. When he saw me he gave the work to his son, who was as brawny as he and always there to assist him, and came towards me, the sweat gleaming on his arms and face. He had a glass counter with the things for sale in boxes below the glass, so that they could be seen but not touched until he took them out. After some hesitation I chose a garnet stone with a painted foil on the underside to make it glow. I thought Sara could wear it on a chain round her neck, or have it set in a ring if she so chose. He asked three silver ducats for it.

Making a purchase often lightens my spirits and it did so now. As I made my way through the darkening streets towards the chapel, my anticipation quickened. I had been following the progress of the mosaics for some years and was on close terms of friendship with the man whose charge it was to see them completed, the Byzantine master mosaicist Demetrius Karamides, who had come to oversee the work by personal invitation of our King Roger.

I entered by the west doorway and the wonder of the place struck me anew, a familiar wonder but one that had never lost its power over me.

The nave was in shadow as I moved forward, but there was lamplight at the far end, in the area of the sanctuary, where they were working. A gleaming light was cast upward on the saints and apostles in the arches of the crossing, holy ranks of those who intercede for us. Light fell on the raised right hand of Christ Pantocrator and on the open book with its message of salvation: I am the light of the world. I could not see the words but I knew them. Christ's face was in shadow but a tremulous radiance lay on the hem of the Virgin's robe and on the gold of her halo and on the outstretched hand of the Angel of the Annunciation. The shadows shifted as I drew nearer and I saw God's fingers and the bright wings of the Dove.

As I walked forward through the shadow I felt that the light beyond was casting for me as an angler might draw his net for a fish to bring it up from the deep. There is no accident in our lives, everything has been foreseen. I had entered at a certain time, in a certain light. There was the open book, the shining disc, the wings; there were the hands above all, hands blessing, hands sending. For a moment I felt the dazzle of a different light, but then it receded and was lost to me. I saw Demetrius move into the light. He came towards me and we clasped hands in the way the Byzantine Greeks are used to doing it, gripping high up above the wrist. He had been more than eight years on the island, first at Cefalu and then at Palermo, yet he had made no smallest effort to adopt the manners or style of dress of his hosts, keeping still the ceremonious ways of Constantinople and the high-necked, loosely belted dalmatic. I had wondered if this were due to pride or a feeling of patriotism, dangerous if so, now that his emperor was preparing for war with Sicily.

Perhaps just an unyieldingness of nature. Or was my own too yielding, too loose? This also I had wondered about. Greek among Greeks, Frank among Franks, what was Thurstan?

I knew as I answered his greeting that something was amiss, not from his face, which was always sombre, but from his tone, from the way he at once drew me aside and led me into the south side of the crossing, out of hearing of the two working in the sanctuary. There was a man slung high against the opposite wall, suspended by ropes on a platform of wood, with lamps attached to the ropes either side. He was working on the decoration on the inside of the arch immediately above the Flight into Egypt. He was very fair; in the light his hair looked golden.

"What is it?" I asked, immediately responsive to this silent guiding of me. As a plant knows the source of light and turns its face there, so I knew the manners of secrecy.

But he said nothing for the moment, merely regarded me. He had eyes as black as jet, high-lidded and very lustrous, compelling in their gaze.