After this not much more was said between us. He accompanied me some way down the aisle but we parted coldly. I stood alone at the door for a little while, looking back down the nave towards the sanctuary and apse.

Where the light fell I could see the coloured marble inlays on the balustrades and lower walls, set like gems on the lid of a casket, work of Italian craftsmen. Beyond this was the radiance of the mosaics. In the dimness above me, hardly visible now but closely familiar from previous visits, was the Arab stalactite ceiling in carved wood, with its painted scenes and Kufic inscriptions. Latin, Byzantine and Saracen had worked together here to make a single harmony, to make this, though still unfinished, the most beautiful church ever before seen in Palermo.

There had been times when the interior had sounded to their separate languages and the chipping and hammering and scraping of their work.

But it was not a question only of the edifice itself. This blending of all that was best in the separate traditions was to my mind a figure for the unity in diversity of our realm, a harmony which our King had known how to protect and preserve. It was my obscure service to aid him in this great task. It was why I struggled to curtail the abuses of the street sweepers. It was why I was going to meet Lazar Pilic.

I cannot say that I found much comfort in these thoughts after the news I had heard and the manner of my parting with Demetrius. I felt heavy-hearted and needful of solace, and as I made the sign of the cross in the shadows before leaving, I thought again about the women of the Tiraz and more particularly about Sara and the gift I had for her in my purse, which would make her welcome the warmer – or so I hoped, feeling the need for her arms about me and the yield of her body.

As I reached the foot of the steps and began to make my way across the courtyard, a man came towards me from the shadows close to the wall. He came on my left side and he was silent and his step was light. The courtyard was deserted and I thought for a moment that he meant to attack me. I swung round to face him and my hand went to the dagger at my belt, that being quicker than a sword to draw and use in the short space there was between us.

"No," he said, "I am a friend, I am Béroul. I was crossing the square and saw you in the light from the doorway as you began to descend the steps."

"Light from the doorway?" I glanced back up the stairway. "You have good eyes."

I saw him smile, as if he knew my thoughts. "I have been wanting to speak with you for some time," he said. "I took the opportunity thus presented."

We were still standing in the shadow of the wall. He was wearing a hooded cloak and I could make out little of his face, except that the smile gave the set of his jaws a famished look.

"I am on my way to a visit of some importance," I said. "Can this not wait until another time?"

"It is something that concerns you closely. You would do well to hear me."

There was a colouring of threat in this, or so it seemed to me. I did not fear Béroul, but if he was prepared to use such a tone, he must deem the matter serious. "Very well," I said, infusing my voice with weariness. "I am listening."

"No, not here," he said. "What are you thinking of? A poor light will not make us less likely to be noticed, ill-wishers can more easily draw near."

"As you drew near to me."

"I am your friend and you will know it soon. If we talk here we will seem like conspirators. If we talk in a tavern I know of, not far away, we are Thurstan Beauchamp and Maurice Béroul, two servants of the Douana Regia, having a cup of wine together and not caring who sees us."

He had used the Latin title of the Royal Diwan with a certain deliberate emphasis, and this, when afterwards I looked back on our talk, seemed the first pointer to his intent. He began to move across the courtyard as he finished speaking and I fell into step beside him without more words.

The tavern was a poor enough place, no more than a cellar, ill-lit and almost deserted – there was a man asleep or befuddled sitting at a table with his head hanging low, and three others playing dice in a corner and disputing among themselves at every throw. The man who served us wore an evil-smelling leather apron and the wine was sour. I was surprised that Béroul should chose such a place. There were taverns in Palermo frequented by the people of the Palace but this was not one of them. We were conspicuous here, I with my plumed hat and loose-sleeved pellice, he with his dark mantle and the fringe and dome of his tonsure – he had thrown the hood back now to reveal this.

He drank a little from his cup, set it down carefully. After a moment he smiled his lean-jawed smile and said, "We have always taken a great interest in you, Thurstan."

"Indeed?" I said. "Is this the plural of majesty we are using?"

"We in the Vice-Chancery, the Magistri Camerarii Palatii. We have been watching over you when little you knew of it."

This I could well believe. "We do our watching too," I said, "we in the diwan al-taqiq al-mamur." I had used the Arab title deliberately and it seemed to me that his face hardened, but there was no change in his tone when he spoke again.

"We have seen your diligence and your devotion to the King's service. It is our opinion that your talents are being wasted."

He seemed to wait for a reply but I made none. After a moment he said, "In spite of your high abilities you will not go far in a douana conducted by Saracens, with a Saracen at its head."

"There are Christians in my diwan, besides myself."

Now, for the second time that evening, I saw a face made ugly by contempt. "Christians? You put yourself on a level with them, you who are of Christian birth? You call them Christians, these filthy palace Saracens that claim to be converted to our faith and secretly continue to practise their own?"

"I have seen no evidence of this," I said, but he did not hear me or showed no sign of doing so.

"Once a Saracen, always a Saracen, it is in their blood," he said. His eyes had a staring look now, that famished smile had gone, and with it all pretence of benevolent interest in me. He leaned forward across the table, bringing his face close to mine. "It is in their corrupted blood," he said, "and they will corrupt our blood with it if we allow them. The terrible warning is there for us in the words of Ezekiel: 'And when I passed by thee and saw thee polluted in thine own blood, I said unto thee: In thy blood live!' The Christian life as lived in Sicily can be summed up as a struggle against contamination, a struggle to keep our blood clean. It is a long struggle, one that has no ending. The threat is always there, no conquest can ever be more than provisional. Tell me, Thurstan, what does Christendom mean to you?"

"It is the term we use for those regions where our Roman faith is predominant."

"That is all it signifies to you? This great spread of our faith no more than a matter of geography? I will tell you what Christendom is.

Christendom is the universal Christian Church, the universal Christian society. Christendom is a mighty host that is destined to bring the world under its sway."

Rarely had I seen such exaltation on a human face. The constraint he was under to keep his voice low intensified the vehemence of his speech. It was quieter now inside the room. The dice game was over, one of the three had left; the head of the solitary sleeper had declined on to the table.

"This Christendom of ours is young," Béroul said, more calmly. "Bear with me, travel back with me in time a little. A hundred years ago almost to the day, you might have seen a company of men making their way from Worms to Rome. If you had been fortunate enough to be of that company, you would have known one of them for Bruno of Egisheim, newly elected Pope Leo IX, another for Hugh, Abbot of Cluny, and the third for Hildebrand, who would later become Pope Gregory VII. Think of it, Thurstan. When, before or since, have three such men travelled in a single company? Three future saints, three men of genius, each dedicated to extending the power and influence of Holy Church. They saw more clearly than ever before that the danger lay in diverse practices, in their different ways they worked to transcend the local, to make our Church one single body. These were the founders of Christendom. Theirs was the spirit that inspired the first crusade and took the Holy Land for Christ."