"I will keep it in mind." I did not tell him I was soon to leave for Calabria; even when we have nothing to hide, the less said the better – another of Yusuf's precepts. Perhaps he had got wind of it somehow, or perhaps his coming to me at this time was no more than coincidence.

"Here is for your trouble," I said, and I gave him two tari from the stock of coins I keep in a box on my desk. "If we bring the dancers to Palermo you will have more."

He seemed well enough pleased with this. Paying for information, something in which I was well-versed, is always a matter of difficult judgement, no matter what the nature of it. If you are too ready, you are taken for gullible, one who will believe anything; if you are too grudging no one comes forward, it is not worth the trouble, or the risk.

Like so much else in our lives, it is a question of balance.

It was in the interest of balance that later the same day I went into the Kalsa, the Arab quarter that lies south of the harbour, riding as far as the Church of San Cataldo and leaving my horse in the square behind the church at stables I had used before: it was better to go on foot and make sure of being unnoticed when visiting Muhammed ar-Rahman.

Here the streets were narrow and the walls high, and the houses had few windows and those closely barred. I walked with eyes cast down, watching my shoes as they scuffled the dust; to look upwards was painful to the eyes in this late afternoon sunlight that came in dazzling reflections from the whitewashed walls. In this district of Palermo there is nothing to tell you where you are, the streets have no names. But I knew the way to Muhammed's house, I had been there before more than once. There was a small mosque in an open space, a simple mesjid with undecorated stone portals and a narrow portico. Close behind this ran a blind alley with a single door. A bell-rope hung at the side. This was the entrance used by those who wanted to keep their visits private; there was another entrance, on a different street, one with wide gates and armed guards. I heard footfalls beyond the door, there was a brief pause while I was scanned through the eye-hole, then the door was opened to me by the enormous Hafiz, who had lost an eye, in what circumstances I had never enquired, and who acted as cook, chamberlain, food-taster and bodyshield. He led me into the courtyard and there I found Muhammed in the shade of the colonnade, half-reclining on a low couch padded with cushions. I heard some notes of a lute and a woman's voice singing low, but this ceased at my entrance.

I felt immediately grateful for the cool here, after the close heat of the streets. Now that the singing had ceased there was for these few moments, as I advanced at Hafiz's side, only the slappings and tinklings of the water from the fountain, as it fell from the tiled niche into the stone basin and down into the channel below.

Muhammed had begun the process of rising, which dignity and corpulence rendered slow. His skullcap and robe were of an impeccable, luminous whiteness. Perhaps my eyes had been affected by the dazzle of reflections outside, because this whiteness seemed stronger than any colour could be, it seemed to draw to itself all the light in the courtyard and even the light from Muhammed's face, so that as he rose to his feet he looked, for all his bulk, strangely like a figure in some theatre of effigies, where only the dress and accoutrements indicate the nature of the personage. This lasted a few moments only. As I drew near his features were restored to him, the short beard, the dark eyes slanting slightly downward like a melancholy dog's, the high-bridged prow of the nose.

"Welcome," he said. "Thurstan the Viking, welcome to my house."

He spoke to me in Arabic, though he knew also Greek, and I answered in the same language, with the conventional invoking of God's blessing on his house. It was his joke to call me Viking, because of my first name which I think derives from the god Thor, and because I am tall and have blue eyes and fair hair that I wear long. It was also a kind of compliment, or at least I took it for such because he thought of Vikings, in their history of seafaring and raiding and settlement, as being a people similar to the Arabs. It was a joke, as I say, but there may have been truth in it; I was born in the township of Norton, close by the River Tees, and that is country where the Danes settled in great numbers in times past, so much so that all that eastern part of England is still known as the Danelaw.

Muhammed made a gesture towards a narrow alcove within the colonnade, where there were low benches against the wall, in the angle of the corner. We sat here facing each other, he against one wall and I against the other.

"You have come on foot, the last part of the way, yes?" he said. "It is hot in the streets, this year the hot weather has come early." He leaned forward and clapped his hands together lightly. "You will take a sarba?"

Hafiz appeared as if by magic. I saw now that he had been waiting out of sight but very close, just inside the arch that led from the courtyard into the interior of the house; from here he could keep us both under his eyes.

I took care to show no haste in accepting this: the alacrity thought courteous by the Franks and the Greeks seems lack of dignity to an Arab.

In fact, I was thirsty after my walk and I remembered Hafiz's sherbet as being particularly good, with just the right mixture of pomegranate and lemon. Nothing much was said as we waited; Muhammed was much too polite to enquire into the purpose of my visit, and I wanted to avoid the appearance of haste.

Hafiz served the sherbet in our full view, pouring from a stoneware jug into the metal cups, making it plain we both drank from the same vessel, a notable piece of hospitable reassurance. When he had again retired, and after some compliments on the quality of the sherbet, I began.

"Yahuda Mari came to us with a complaint some days ago."

"Yes?"

"He came in person."

"I see, yes, a serious matter." Nothing had changed in Muhammed's face.

"There is a complaint that some Jewish cemeteries have been broken into during the hours of night and damage done to the graves."

Muhammed made a brief humming sound, perhaps to show interest or perhaps merely to encourage me in my narrative. He was leaning back comfortably against his cushions.

"Following upon this there is the further complaint that members of the Jewish community have had money extorted from them under the threat that their family tombs will be desecrated if they refuse to pay. According to Yahuda this has been going on for some time, but the people were too much afraid of injury to come forward."

Muhammed nodded, with a full appearance of understanding. "That is often the reason for silence."

After a moment's pause, in a tone I took care to keep dispassionate, I said, "It seems that these threats come from Arabs."

"Do they say that? Surely Yahuda himself has not been threatened?"

"Of course not." He was prevaricating now, and he knew that I knew this.

The Mari were an ancient and powerful family with their main strength in Marseilles but with trade connections throughout Italy. Yahuda was the leader of the Palermo Jews, a man of great wealth. "Who threatens Yahuda?" I said. "We do not threaten the strong but the weak."

"My Viking, you speak with the simplicity of youth. When you have fullness of years you will know that the strongest are those that can be threatened most, because they have most to lose."

"He came to speak on behalf of his people. And it came to the attention of our diwan because no taxes or dues are paid on sums deriving from extortion, and so there is a possible loss of revenue to the Crown.

There is also the question of preserving harmony between races and religions. Yusuf ibn Mansur, who sends his warmest greetings and God's blessing upon you, asked me to seek your advice because of the close friendship that is known to exist between us."