Orm said mildly, 'But the Christians are strong now.'

Ibn Tufayl was dismissive. 'Let me tell you the truth about Christians in al-Andalus. Have you heard of the Martyrs of Cordoba? Christians have always been tolerated here, as you are dhimmis, People of the Book, like the Jews. But these "martyrs", fifty or so, began to challenge the authorities, and to insult Islam. In the end they got what they wanted: a glorious public death. Such self-sacrificing idealists are trained in the Christian monasteries, which we continue to tolerate in our territory. Hotbeds of violence and rogue clerics and the extreme preaching of hate. Thus it goes when an inferior civilisation, yours, meets a higher one, ours. Your only weapon is your own petty lives. But these attacks are pinpricks. Nothing.'

Orm said, 'I don't think I would call the loss of Toledo a pinprick.'

Ibn Tufayl smiled. 'It is a setback. Nothing more. There is talk of summoning help from across the strait. In the Maghrib there is a new movement called the Almoravids. Fierce, strong Muslim warriors. It won't be long before the old city is in the hands of an emir, and the muezzin rings out across the rooftops once more.'

'We'll see,' Robert said, and he glared at the vizier, who laughed at him.

After more talk of this sort, with Ibn Tufayl pressing Orm over details of what he called Viking ways of life and of making war, the little meeting broke up. They were all dismissed, save for Sihtric, who said he had business to discuss with the vizier.

'I'd like to know what kind of "business",' Orm muttered to Robert.

'I don't think I'd trust that vizier,' Robert said. 'He had wine on his breath. Muslims don't drink.'

'No, they don't. Or aren't supposed to. There's more to the vizier than meets the eye. And I'd like to know more about the relationship he has with Sihtric. What hold does Sihtric have over him?' Orm sighed. 'I suppose it was foolish to think there would be anything simple about all this. Sihtric is a complicated man, and this is a complicated place.'

'But you're going to try to resolve your business with Sihtric even so?'

'I think I have to. I'm going to wait here for Sihtric. What will you do?'

Robert grinned. 'Go back to the city with Moraima.'

Orm nodded. 'I thought so. Just be careful.'

'My arm is strong.'

'But your heart isn't, no stronger than mine ever was. Be wary, son.'

'Take your boots off,' Moraima whispered.

They stood in the walled courtyard of Cordoba's great mosque – the Court of the Orange Trees, Moraima called it. It was crowded with the faithful, who washed in the fountains before entering the mosque.

Robert peered nervously through a narrow door into an interior of shadows and columns. 'Are you sure about this? This is a mosque – I'm a Christian-'

'But Jesus is revered in our theology. He was a great prophet. Of course a Christian may enter a mosque.'

'Besides, the mosque is the greatest religious glory of all al-Andalus,' said a boy, approaching them. 'You must see it before you come to conquer us, Christian.'

And a second boy said, 'Just don't go shouting out "Jesus Christ the King" in the Mihrab and you'll be fine.'

These two were about Moraima's age, perhaps a year or two older than Robert. They were slim, dark, dressed in brightly coloured clothes. Healthy, loose-limbed, they were not especially handsome, but they seemed intelligent, good-humoured, confident. Even their Latin was fluent. And they had the air of wealth, of easy riches. Before them Robert felt dull, cloddish, like a lump of earth.

'These are my friends,' Moraima said. 'Ghalib. Hisham.' Robert wouldn't have remembered which was which, save that Ghalib wore a bright red turban. They were sons of courtiers who served Ibn Tufayl, she said.

'I didn't know we'd have company,' Robert said, and he struggled to keep the disappointment out of his voice.

The boys noticed, and they grinned. But what had he expected? Of course Moraima had friends here; of course she had a life of her own, that had nothing to do with him.

Moraima said, 'Oh, come on, Robert. I thought you'd like to meet new people. And they've been eager to meet you. Hisham is studying philosophy, and Ghalib's training to be an astronomer, like his father.'

Ghalib said the word slowly and heavily. 'Astronomer. I don't suppose you have many of those in England, do you?'

'You'd better write it down for him,' said Hisham. 'Oh, I forgot. You don't read in England either, do you? So what do you do, English Robert?'

Ghalib said, 'There are only two jobs in England. Farmers and whores.'

Robert said tightly, 'Watch your mouth, pretty boy. My mother was English.'

'So what kind of plough did she drive?'

Moraima stood between them hastily. 'That's enough. You're like children – like all men! Come on. Let's go into the mosque, and be respectful with it.'

So Robert entered the great mosque, with Moraima at his side, the stone floor cold under his bare feet, and the two boys sniggering at his back.

But in the mosque's calm spaces, he soon forgot all about the boys.

It was like walking into a forest of slim pillars, linked by arches as delicate as the fronds of palm trees. Moraima said there were more than a thousand pillars in this one building. There were people walking everywhere, respectful, barefoot. Not a priest, or rather an imam, to be seen. The building was full of light, coming from windows and arched doorways, a light turned golden by reflection from the stone. Every way he looked the lines of pillars led his gaze away, deeper and deeper, until he saw walls adorned with inscriptions in beautiful Kufic script, words he could not read but which exhorted the faithful to raise their hearts to Allah.

He was grateful when Moraima's hand slipped into his, for he felt he would soon be lost.

'What are you thinking?' Moraima asked softly.

'That it's beautiful,' he said. 'And that I don't understand it. Of course I could say the same about you.'

She ignored the clumsy compliment. 'It isn't so hard. There is a central axis leading to the Mihrab. That points the way to Mecca; there the imam calls the faithful to Friday prayer. But you may pray wherever you like. The priests don't get in the way here. My father says it's a "different geometry of worship" from the Christian.'

'This is nothing like a Christian church.'

'Well, no. Christians build their churches as Romans once built their basilicas. That's what my father says. The first emirs of al-Andalus started with nothing. They borrowed ideas – the round arches of the Romans, for instance. They even reused what the Romans and the Goths had left behind.' And she showed him how many of the columns, of jasper and marble, were subtly different, in their proportions, their capitals; they were Roman and Gothic relics.

'The arches are meant to look like the branches of palms,' Moraima said. 'It is an oasis in stone.'

'Yet it's centuries since your people came from the desert.'

'Yes. We were thrown down here and changed. Isn't it funny? Now we are not African any more, but not European – just us, something different in the world…'

They walked further, and Robert learned to read the history of al-Andalus in the slim columns of stone.

At first the Muslim conquerors had been in a minority, a few hundred thousand in a Christian population of millions. But that proportion grew quickly, thanks to massive immigration across the straits from Africa. And though tolerance of religion was practised, Islam was the religion of the state, and conversion was a useful step on the road to power. Ibn Hafsun's family had been one Gothic dynasty who had abandoned the cross for the crescent. And as the numbers of Muslim worshippers in Cordoba grew, so the great mosque was extended several times to accommodate them – most recently by al-Mansur, the overreaching vizier who had brought the calamity of the fitnah upon al-Andalus.