Her face illumined by the fireglow, I had a moment to assess this beauty that had so bewitted Uther. She was, perhaps, all of fifteen years. Tall, slender, her finely-formed head borne gracefully on an elegant neck, she lacked the awkward girlishness of her age and appeared far more mature. Nor was appearance deceiving: Gorlas' wife had died when the girl was still a babe and she had been raised from childhood to be the lady of the realm.

This I learned later. At the time, I saw only a comely girl with soft-woven brown hair and large dark eyes, in whose pretty smile a man might gladly lose himself.

'Will you be announced?' I asked Gorlas.

'Are we not expected?' he answered hotly, then turned to me. 'Oh! it is you, Merlin… ' My name was spoken like an oath. He worked his mouth silently, and at last forced out, 'As you think best.'

No, Gorlas wasted no love on me. But he respected me, and no doubt feared me a little – as any lord fears the man closest to his ruler's ear. 'We will go in together then, since -' I began.

'I will see to it,' Uther said, shoving between us. He turned Gorlas by the arm and led him off across the courtyard. I watched the three of them walking between the leaping flames of two fires and I saw Ygerna step lightly between Uther and Gorlas. Everything froze in my sight, all sound and motion ceased, vision narrowed as in that instant a deathly foreboding awakened within me. Nothing else existed but the terrible vision before me:

Ygerna between two kings.

Here was the nameless danger I had felt earlier in the day, redoubled in force. Ygernal Oh, fair daughter, in your hands rests the future of the realm. Tonight you are destiny's handmaiden. Do you realize that?

No, of course she could have no idea. There was virtue as well as nobility in her rearing. Her natural innocence prevented her from using her beauty as a less scrupulous woman would have. Another year or two older, and I might have been seeing the end of the world stepping so lightly between the coronation fires.

I made my way after them, stumbling, numb, coming into the hall as they approached the High King. Uther worked to his brother's side. Aurelius welcomed him, clapped him on the back – I think that until this moment the High King had not a thought to spare for his brother – and thrust a drinking cup into Uther's hand. Uther took the cup, drank, and passed it to Gorlas, who proclaimed his loyalty to the High Kingship.

Then Aurelius' eyes fell upon Ygerna. I saw him smile. I saw the change in his nature as he beheld her. Perhaps it was the giddiness of celebration, or the play of light upon her face, or youth calling to youth, or merely the wine running strong in Aurelius' veins. Perhaps it was something more… But I saw love kindled in that first brief glance.

Alas, I was not the only one to see it!

Uther stiffened. Had he been a porcupine he would have bristled. His grin froze on his face and the light died in his eyes. He seemed to grow visibly smaller as he stood in his brother's shadow.

Oblivious, Aurelius made a gentle remark. Ygerna lowered her eyes and laughed, shaking her head in response. Gorlas placed his hand on his daughter's shoulder and drew her forward. A minute gesture, imperceptible perhaps to anyone else, but I saw it and read well its meaning. Whether he knew it or not – I do not say that he did – Gorlas was offering his daughter to the High King.

And Aurelius, dear blind Aurelius, unaware of his brother, accepted her with the whole of his heart. He offered Ygerna the cup and his fingers lingered at her hand. Ygerna glanced meekly at Uther.

That look might have saved much, but Uther did not see it. He stared ahead dumbly – a man whose head has been severed from his body in a single stroke and knows for certain that he is dead and now must fall.

Then Aurelius bent near and whispered something to Ygerna. She smiled shyly and Aurelius threw back his head and laughed. This could not be endured; Uther turned on his heel and flew from them, disappearing into the roister. Ygerna looked uncertainly after him; her hand fluttered out to where he had been. But Uther was already gone and Aurelius was speaking again and Gorlas, holding his cup high, was beaming with delight.

I felt as if I had been kicked in the stomach by my horse, as if the floor had become unsteady beneath my feet, as if I had drunk a very powerful draught that confused the senses. The room spun and all became sharp noise and sharper light. Pelleas was suddenly there beside me. 'Master, what is wrong? Are you ill?'

'Take me from here,’ I whispered. 'I cannot breathe.' A moment later we were standing outside in the crisp, cold air. My head cleared and sense returned, but I was left with the sick feeling of deepest dread. What had been lost? More to the point, what could be saved?

I marvelled at the speed with which it had happened. How could I have foreseen it? Oh, but I should have known. I had been warned – out on the road my danger sense had been aroused, but I had not looked for the cause. Come to that, I had been amply warned in Celyddon. Nevertheless, my only thought had been to get the crown securely on Aurelius' head. I had looked no further than that.

It is strange that when a man spends all his time fighting one enemy, he fails to recognize another, greater foe. I knew him now, but it was too late. The damage was done. The Saecsen battles of last summer would dim in men's memory before I finished righting the destruction of this night. Great Light, we are not equal to the fight! Pelleas held me by the arm. 'Laid and master, are you well?' The concern hi his voice was like a slap. 'What has happened?'

I drew a deep, unsteady breath. 'The world has tilted from its course, Pelleas.'

He stared – not in disbelief, but in sympathy. 'What is to be done?'

‘That I cannot say. But we will be long repairing the breach, I fear.'

He turned his head and looked back into the feast hall, where the High King stood with his lords. Gorlas and Ygerna had moved away to find their places at the board. The food was being served now and it would have been sweet delight to have forgotten, if only for a moment, that what happened had ever taken place.

But that is not how the world is made. Once spoken, a word cannot be called back; once loosed, an arrow cannot return to the bow. What happens, for good or ill, happens for ever and that is the way of it.

The feast proceeded, but I had no appetite for it. I left Pelleas to watch for Uther, knowing he would not be found, and slipped away to my room. There was nothing to be done.

I did not sleep well and rose with a throbbing head and a bitter taste in my mouth. The sun was rising on a grey, rain-swept day. Londinium lay strangely quiet; most of its citizens must have found their rest but late and were still abed. From the church nearby I heard the light tolling of a bell. The brothers were telling Prime and would soon be at prayer.

I rose, threw my cloak over my shoulder and went down, slipping through the silent house, and across the wet yard to the church. I pushed open the door and entered. A number of monks were kneeling before the altar and I started towards them.

'Merlinus!' The whisper echoed in the room. Several of the monks turned round to look at me. I stopped and Urbanus hurried forward, his sandals slapping the stones at his feet. 'I did not think to find you here. I was about to send for you."

I heard the note of strain in his voice. 'I am here. What is it?'

'It is Dafyd,' he said. 'Come with me; I will take you to him.'

Urbanus led me out across the inner court to the cells. Monks had gathered outside one of the doors. They parted when we came up, and Urbanus ushered me into the room. Dafyd lay on a pallet of fresh straw in a room illumined by a candle tree brought from the altar. He smiled as I came in and lifted a hand in greeting. Gwythelyn was with him, kneeling beside him, praying; he turned to me and I understood from his grave expression that Dafyd was dying.