More than thirty of the queen's warriors had been captured – attesting to the utter surprise with which the city had been attacked. No man, from the highest warrior to the lowest stablehand, would ever have allowed himself to be taken alive if he had weapon to hand, or, failing that, a chance to swing his fists.

The waiting warriors stood with their heads bowed in disgrace, hands bound, surrounded by Picti guards. Smoke rolled across the yard and coiled from numerous sites within the city. Shrieks and screams echoed in the distance. I was brought to stand with the other Britons and after only a few moments saw the Emrys and the Queen roughly dragged from, the palace. The sight of Myrddin and Gwenhwyvar, bound and hooded, the hands of the enemy upon them, made the gorge rise in my throat. I retched and choked back bile. The tears welled up in my eyes.

Medraut, his expression wild and fantastic, strutted forth across the yard, a big Pict battlechief on either side of him. He was no true warrior himself, so moved only in the company of warriors. In truth, he was nothing more than a cunning coward.

Upon reaching the place where the captives waited he uttered a sharp command in the barbarian tongue. All at once, the Picti raised blade and spear and began stabbing the hostages. Brave men fell all around me. I saw more than one sword plunged into the belly of a defenceless man, and that man fall to his death without a sound, courageous to the end. One battle-scarred veteran even seized the sword as it swung towards him and with a defiant cry thrust it through his own heart rather than allow the enemy to kill him so shamefully.

I was struck to the ground and pinned there with the point of a spear. When the slaughter was finished, only eleven remained. Medraut saved the most important of his captives for the hostage pits: the queen, the Emrys, myself, and eight others whose fives he hoped to bargain with.

Let him do his worst. That day I watched good men die and pledged my life to seeing Medraut's headless corpse torn to pieces by the High King's hounds.

I was thrown into a loathsome pit beneath the roots of the fortress. There with some few of the other hostages I stayed. Whether day or night, I knew it not. Where the queen was held, or what had become of the Emrys, I could not say.

Occasionally, we were hauled from the pit and made to parade in chains before our Picti captors who wished to boast of us before their chieftains. At one of these times I discovered that we were enjoying the hospitality of Keldrych, a powerful Pict king, who had succoured Medraut when the tyrant fled Arthur's fosterage.

Keldrych summoned the fierce tribes of the north to attend him in Caer Lial, there to see for themselves how he and Medraut had seized the Pendragon's city. Word of rebellion spread like plague among the Picti, who had never loved Arthur and needed little enough encouragement to break faith with him.

A blind man could have seen what was happening! Having stolen the queen, the traitor bargained with the lords and battlechiefs of other Picti tribes for support. And this he won.

Curiously, the Picti, among other primitive peoples, consider the kingship of a lord to rest in his queen. The king's wife is the living symbol of his reign. It is a belief ancient beyond reckoning, and more enduring than stone.

For this reason, the Picti were much impressed with Medraut's abduction of Gwenhwyvar: she was Arthur's kingship. As Medraut possessed her, so he possessed the throne of Britain. To the Picti this was self-evident. In seizing the queen, Medraut had made himself king, and in their eyes proud Gwenhwyvar became Medraut's wife. This treason moved the Picti as nothing else could. In treachery was Medraut the master.

Arthur, of course, was expected to return and fight for his throne. Medraut meant to be ready. With extravagant promises and subtle deceptions he wooed the rebel kings. As the summer waxed full, the forces of the Picti gathered for war. With each day that passed the enemy grew stronger, as more and more warbands arrived in Caer Lial, summoned by Keldrych and Medraut, and emboldened by the prospect of Arthur's defeat.

From the wild hills of the north they came – from Sci, from Druim and Gododdin, Athfotla and Cait. They came by the hundreds, gathering together in a mighty host, separate tribes united only by their quick-kindled hatred of Arthur, and the promise of enormous wealth through plunder.

At the riotous Lugnasadh celebration the hostages were once again dragged out to parade before the assembled battlechiefs. The sight of them nearly stole the breath from my lungs. Gathered in Arthur's hall was an immense host of blue-painted Picti lords, each and every one a chieftain with many hundreds of warriors in his keep. Never had such a host been assembled in Britain, I thought; surely the Pendragon cannot match such a force.

To our disgrace, we were made to serve our captors meat and drink and endure their crude sport as they viciously shoved us and choked us with our chains. When the riot reached its height, Medraut rose up and with much demonstration spoke to the assembled chieftains. I do not know what he said, but that night we were not returned to the hostage pits. We slept in our chains in a storeroom and the next morning were taken out into the yard.

The hostages were herded together and, to my joy and relief, I saw that the Emrys and the queen remained unharmed. I had not seen them since the fall of Caer Lial and had feared for their safety. Although the queen was held a little apart from the rest of us, I was encouraged to see that she appeared defiant and unbowed, full of fire. By stealth I managed to creep near to the Emrys.

'Emrys, are you well?' I asked.

'Well enough, Aneirin,' he answered, his voice low and raw. 'And you?'

'I have not been harmed – nor have the others,' I replied. 'Do you know what is happening?'

'Arthur is returning,' the Emrys told me. 'Word came to Medraut a few days ago that the High King's fleet had been sighted. Today the battle will be joined.'

These words heartened me, but I noticed they brought no cheer to the Wise Emrys. 'But surely this is good news,' I said. 'What is wrong?'

'We have endured so much and laboured so long to be undone like this,' he said, 'and you ask what is wrong?'

'Arthur will not fail.'

The Emrys regarded me long, his golden eyes deep-shadowed with sadness. 'Trust God, Aneirin. And pray that the sky does not fall upon us.'

I crept away, confused and dismayed. All I had suffered till now was nothing compared to the despair I felt in the Emrys' few words. For the first time I began to sense something of the magnitude of Medraut's treason. My heart broke, and my soul cried for leaving. I was that unhappy.

After a time, we were marched through the city to the harbour, where some ships were arriving from Orcady. I little guessed that Lot was in league with Medraut but, to his everlasting shame, Lot did nothing to aid the queen. Instead, in the full view of all, he waded to shore with his chieftains and embraced the tyrant like a kinsman.

'How can he do this?' I wondered aloud to the Emrys as we squatted on the shingle. 'I thought Lot was Arthur's ally.'

'Do you not see it yet?'

Once again I was forced to admit that I did not. I had no idea what Myrddin was hinting at. 'You mean Lot has joined the treason?'

'Do you not know Medraut even now?'

'He said he was the son of a Picti lord – Urien of Monoth. That is what he said when he came before Arthur,' I answered.

'He is no Pict,' snapped the Emrys. 'Think! Did you not see how they treated with him, and how he wheedled and schemed with them?'

'I was in the hostage pit!' I reminded him. 'I saw nothing.'

'Medraut is Mdrgian's son!' The Emrys answered my disbelief with a further revelation. 'And the man greeting him on the shore is not Lot, it is his half-brother, Urien.'