When displeased he had a way of lowering the lids over them that gave his face an expression of suffering not patiently borne.

"Is the work not proceeding well?"

"We will not be permitted to finish the work. We will soon be leaving here."

"Leaving? But there is so much still to do. There is the west wall, and the arcades and the apostolic sequence in…"

"Yes, as you say, there is much to do still, but it will not be my people to do it, new people will be coming. We will finish the mosaics in the sanctuary and the crossing because they do not want so evident a mixture of styles, but we will be leaving before the end of the year."

"New people?" I was bewildered. "Who are they that do not want mixed styles?"

Demetrius indicated with a movement of his head the man on the platform high on the north wall of the crossing. "He is one of the new ones. They are Latins from the north, Franks. We set this one to do the fleurs délices decoration on the arch because it is all we can trust him to do."

I glanced upwards. There was an aureole of light around the man's head; he was like a heedless angel, suspended there with his back to us. To the right of him, level with his shining head, were the emerald fronds of the Egyptian palm and the infant Christ sitting upright on Joseph's shoulder. When I looked back at Demetrius my sight was dimmed for some moments, as if I had been looking into the sun. "It cannot be," I said.

"It cannot be to replace you that they are sent. To work with you, to learn, yes. You are known for a master, you made the mosaics at Cefalu for our King Roger, and all of us know how much they pleased him."

The King's gratitude had been lavish: five hundred gold dinars as a gift on the completion of the mosaics, this sum in addition to the wages and the maintenance written in the contract. I knew this for a fact, as the accounts had been drawn up in our Diwan. "There must be some mistake," I said.

Demetrius made the strange, angular gesture of the Byzantine Greek, angry and resigned at the same time, shrugging his right shoulder and slightly raising his right arm, palm upwards, as if throwing some object awkwardly up into the air. "There is no mistake. Unless it be the mistake of employing lesser craftsmen in our stead. We have the wrong liturgy, the Latin Christians will take our place."

"By whose order?"

"By order of the King."

I was dumbfounded at this; in fact for some moments I could not believe the words had been said. A long course of persuasion and many promises had been needed to bring Demetrius Karamides to Sicily. In Cefalu first, and now here in the Royal Chapel, in the apse and sanctuary and crossing, he and those he had brought with him from Constantinople had made mosaics that were the wonder of the world. Whose the skill of tongue that had persuaded the King to order this dismissing of them? It could only be as Demetrius said, those of the Roman Church, wanting mosaic workers of their own liturgy in this place where the Latin mass would be celebrated. But what filled my mind, once the shock of surprise was over, excluding all else, was the fact that this decision had been taken and these orders carried out without the smallest trickle of information reaching the Diwan of Control – not even rumour had come to us. This it was that gave me the beginnings of fear as I looked beyond Demetrius into the shadows of the nave. Such secrecy was the mark of power. By what paths had they reached it?

"It cannot be," I said, but I was speaking now of this discord, this enmity of faiths, here where Saracens had carved the wood of the ceiling, Latins made the marble inlays, Greeks set the stones of the mosaics, all working together to make a church where our Norman King could hear the mass.

Perhaps hearing the trouble of my spirit in my voice, Demetrius moved towards me and again took my arm. "Come this way a little," he said.

"You cannot see well in the lamp light. Not well enough to make a full judgement. But the medallions in the soffits of the arcade here, these were done by our people, working alongside Lombards from the mainland.

Working together, you understand? The work is fine, just as it is in the apse and the sanctuary and the side chapels. They worked well but it was always under our guidance. They have learned but it is not yet enough.

Now these newcomers, who know even less, will have charge of all the work in the nave. You will see how the mosaics will be coarsened, they will hold less light."

His eyes opened wide as he spoke. "Light," he said, "the art of mosaic is the art of light. It is in the setting of the pieces, not in the colour. We see where one colour ends and another begins, but light is splendour, and splendour has no bounds. Who does not know how to catch the light will never make truly fine mosaic. Their work will never be as ours here. You will see where our work ended and theirs began."

He had spoken with much feeling and his eyes, as he opened them full upon me, gleamed in the lamplight as if they too had caught the light he was extolling. But it seemed to me that he was exaggerating because of his hurt at being supplanted – a feeling natural enough. I could not believe the King had allowed himself to be persuaded to entrust the mosaics of his own chapel to people of inferior skill, knowing them for such. Demetrius spoke as if there were no other makers of mosaic in the world.

"Yes," he said now, "in all the time to come, while this church stands, they will see where our work ended and their coarser work began. That is a consolation to me, that it will be seen and known through all the ages."

"Demetrius," I said, "please believe me when I say how unhappy this news has made me. I will try to discover more about it. There must be reasons, urgent reasons, that we know nothing of."

I had spoken these words with eyes cast down, as is the custom among us when we share the sadness of others or commiserate with them in loss or misfortune. When I looked again at Demetrius' face I saw that its expression had changed, a smile had come to it but not a pleasant one.

"The urgent reason we know nothing of is that your King wishes to please the Bishop of Rome by filling all offices with Latin Christians. He hopes that this, if continued long enough, will gain him the recognition of Rome, which so far he has failed to obtain."

There was almost a sneer in this, something unusual in him. I was offended by the slight on our good King Roger, especially as there was some small part of truth in it, not as regarded his motives – of these what could either of us know, who were so far beneath him? – but in the fact that Pope Eugenius still continued to address him as Signore, unjustly withholding recognition of his royal title.

"I believe the King has been deceived," I said. "He has been advised wrongly."

"What does it matter how he was advised? He has set his seal on it. You will have the decoration of the nave arcade, on both sides. You will be obliged to keep to the book of Genesis – that was agreed on all hands when we started our work here. But you will turn it into stories."

His face was close to mine as he spoke and I saw his mouth twist with contempt. "It is all that you of the west know how to do. You go from left to right, from one scene to the next, in a line. You have no understanding. God's grace is not different from his power, they fall from above to below, one face of splendour, like the light. And this grace and power, what do you do with it? You make stories. God creating light, a little figure in the corner, making a gesture, then we move on to the next scene. God lives in the light he creates, but you do not know this, you make stories."

The contempt was in his voice and it was for me also. I had never heard him speak in such a way and it made me think I did not really know him, though for years I had counted him as a friend. His pride had been hurt, yes, he had suffered a heavy blow. But the contempt had been there already, some lesser blow would have brought it out. When there is a flaw, any tremor will break the rock asunder. I think it is St. Paul who says this, in his Epistle to the Thessalians, exhorting unity of faith and practice among his brethren in Christ. But it was only later that the words of St, Paul – if indeed it was he – came to my mind. What should have made me sad, had I been wiser, only made me angry now. I said, "It is usual in those who lack a thing to be jealous of those who possess it. God's revelation is made known to us by unfolding, like turning pages. We have the gift of narrative, you have not. So you make it a fault in us."