I felt utterly useless as I watched them prepare for the single combat. I tried to cross to Melwas, who had picked herself from the floor, and taken her place behind Palomides, but Merlin held me back.

'No, no, lord of the lake,' he said in my ear. 'Simply remember: as soon as I have my spear you will forget all this, and your life will be most pleasant.'

Hermann the Sessite had shed most of his furs, and was picking his hairy nose while he waited for his young opponent. He examined his finger and rolled what he found there into a ball, which he flicked towards his men. Mordred, Piers and Aglinda were around Alisander. Mordred was kneeling before the boy, talking to him very calmly. Every few moments Alisander nodded to indicate he understood. Aglinda's hand gripped the stained cloth of her friend's undershirt. She was utterly distraught. But the brave boy paid no heed to her, concentrating only on Mordred's words.

Behind them, Iseult and Queen Melody had come together. Elia was pacing around beneath the gates, scuffing up dust and singing snatches from different songs. She made them seamlessly transition into each other, as if they'd been the same song all along:

Thus actor of Athens he saw not her lies

As she took out her knife and put out his eyes

With an M and an A and an R and a K-o

That's blind King Mark of TintagHell-o

Eyes look on masks

And thrill in deceit

Eyes behind masks

At TintagHell-o

Something occurred to me, or, really it was many things at once. I looked up to the top of the battlements, where the king of Cornwall remained flanked by his two loyal knights. I breathed deeply.

'Q-Q-Queen Melody!' I cried at the top of my voice. All around curious faces swivelled in my direction. 'Q-Queen Melody, is it t-t-true?'

The babble of the soldiers, who had been discussing whether it was worth placing bets on the outcome of the combat between the Sessite general and the boy, died down.

'Is what true, Drift of the lake?' replied the queen.

'Is it t-t-true that you husband b-betrayed the people of his southern c-c-coast to the Sessites, as A-Alisander accuses him?'

The queen blinked. 'Aye, it is true, alas.'

'And is it t-t-true that he b-bargained with the raiders; that he b-bought their meat and c-c-corn in return for his own s-safety?'

'Aye, alas, it is true.'

There were gasps from the battlements. Some of the archers ranged along the wall turned to observe their king's reaction. Mark simply stared down at me, his expression unreadable.

'Enough of this! Enough!' cried Merlin by my side.

'Then it is t-true that k-k-king Mark, who so p-prides himself on oaths and v-v-vows, is himself an oathbreaker? That he b-broke his m-most sacred oath to his p-p-people?' I shouted over the sorcerer.

Melody did not reply this time. She bowed her head. But the effect on the wall was the one I had hoped for. Sir Bersulus turned to his king, a look of horror on his face.

'I said enough!' shouted Merlin, and at once I felt myself paralyzed. I breathed, but I was unable to speak or otherwise move. I struggled against the wizard's magical grasp, but could not free myself.

'The single combat!' shouted Arthur, giddy with excitement. 'I would see the single combat!'

On the battlements, Sir Amant had placed himself between Mark and Sir Bersulus. Few of the archers had resumed their positions; indeed, they were starting to gather behind their king on one side, and Sir Bersulus on the other.

'Begin! Begin!' Arthur waved Hermann the Sessite on.

lifting his huge double-edged battle-axe above his head, the huge man ran roaring towards Alisander.

Mordred nodded a final time to Alisander, and dragged the weeping Aglinda away from the boy, though her fingers were fastened so tightly on his shirt that it tore. Alisander turned to face the barbarian, who was three times as tall and several times as wide him. The point of Excalibur rang on the stone as the boy dragged the heavy blade in a circle along the ground. It did not seem as if he was strong enough to lift the blade. The Sessites cheered in cruel bloodlust as their general leapt, his axe high above his head, ready to end the bout in a single blow. I held my breath. It was all I could do: Merlin's magical grip would not allow me to close my eyes or turn away. The edge of the axe swung down towards the boy's head, ready to split him clean in two.

At the very last moment, Alisander hauled the glowing sword from the ground so it was upright, partly defending his face. It was not enough, I thought; Hermann's weight and force would simply drive the sword back into the boy's flesh.

''Sander!' I heard Aglinda scream most of his name, but the last syllable was obscured by a strange noise like a badly tuned bell, made by the striking of the axe against the metal of Excalibur. Hermann seemed to reverse in mid-air. His axe shattered in several pieces that fell around Alisander's feet like so much dust. The man was thrown twenty feet from the boy, almost to the feet of the stunned British soldiers, some of whom covered their ears against the horrible sound. Hermann writhed in pain, clutching his left arm as if it were broken.

Still holding up the sword before him, Alisander advanced on his opponent. Excalibur wobbled in the air, but there was no fear in the boy, only determination. Hermann struggled to his feet, let go of his arm, and fumbled a long knife from his belt with his right hand. The point of Excalibur dropped, and Alisander charged, ready to run the blade through the man who had killed his father. The boy screamed his rage.

For a moment the scene disappeared from my eyes; Arthur had blocked my view. The king bobbed out of my sight for a moment, leaning down, and then leapt to the right, wrenching his arm in the direction of the duel. Excalibur's point was mere feet from the Sessite's belly. Horrified, I saw that the king of Camelot had thrown a stone that he'd picked from the ground. It was flying in a swift, perfect arc towards the back of Alisander's head.

The Sessite crouched, ready to attempt an evasion of Alisander's attack, but before the boy could close the last couple of feet, Arthur's stone found its target. Alisander toppled flat on his face and Excalibur clattered from his hand, coming to rest at the Hermann's feet.

The Sessite took immediate advantage of the situation, and plunged his long knife into the child's back. He withdrew it, and prepared to stab again.

'STOP!' roared Mordred. 'He yields! He yields.'

Hermann froze, the bloodied knife raised above his head. Aglinda broke from Piers' arms and raced towards the prone boy.

'That was not just!' cried Mordred, approaching his father. 'That was not right! We agreed to single combat, not to this, this travesty.'

'I don't know what you're talking about,' said Arthur. He moved his head from left to right, expecting the watching men to laugh at Mordred's imagination. But they had all seen it, every one of them.

'You interfered,' said Mordred. 'You threw that stone.' He grabbed the king by the scruff of his neck, dragging his father's face to his.

Beyond them, Aglinda turned Alisander over. He was bleeding from his chest as well as his back, and was either dead or unconscious.

'I demand that we fight,' roared Mordred. 'You and me. Right now.'

'Unhand me, boy,' laughed the king, regaining some of his composure. He pushed Mordred away, and began straightening his clothes. 'The duel is done: you yielded on that boy's behalf. My champion is victorious.' He looked to the Sessites, expecting a rousing cheer, but all he got from the barbarian raiders was a stunned silence.

In floods of tears, Aglinda dragged Alisander back towards the gates. Piers advanced, and took the bleeding lad up in his arms. He too was weeping. I wanted more than anything to break free of my bonds, to see what the watersnakes could do to save the brave boy, but I couldn't move.

'You say I threw a stone,' said Arthur at the top of his voice. 'Well I didn't see anything. Did you Tristan?'

Sir Tristan looked at his king and said nothing. I think even he was ashamed of Arthur's actions.

'You, Gaul? Sir Palomides?'

Melwas' mouth trembled. She was trying to speak, to deny Arthur's version of what had happened, but she could not. She was as trapped by one of Merlin's spells as I was. Palomides, who had experienced the terrible pain of Merlin's tortures first hand looked at the ground and said nothing.

'Did you, lads?'

No one from Arthur's army of Britons made a sound.

'What about you, Mark?' he shouted, bending his neck to speak up to the battlements. 'Did you see anything?'

king Mark stood in silence for a long moment.

'My king, please,' begged Sir Bersulus.

'No,' said Mark, defeated by both his madness and his cowardice. I believe he would have told his rival that sun was black if it had meant the world remained as his disordered mind had arranged it. 'No, Arthur, I saw nothing.'

Arthur smiled at Mordred in triumph. 'You see?' he said. 'Or rather, you don't see. Heh.'

At that moment Mordred broke across the ground where Alisander and Hermann had fought, heading for Excalibur, which still lay on the ground. Merlin nodded his ram's skull staff in the direction of the green blade, and before Mordred could reach it, a cage of bones shot from the ground and encased the blade. Mordred pounded on the bones with fists and feet, but they would not shatter. Iseult left her place by the gates and walked slowly to her brother. His fists were bloody from battering the cage. Iseult twined her fingers in Mordred's curls, leant down, and kissed her brother on the top of the head. She whispered something in his ear, and her touch and her words stopped his frantic struggling. Iseult brought him to his feet, and hand-in-hand brother and sister walked back to the gates, where Piers had laid Alisander in the shadows. The front of the farmer's smock was soaked in the boy's blood. Aglinda knelt by the lad, pressing his limp hand to her face.

'God has spoken!' cried Arthur. 'The May-children forfeit their lives.' He sidled over to Sir Tristan. 'Kill them, my friend, though take the pretty girl if you like.'

'With pleasure, my king,' said Tristan, a dirty grin on his face. The knight drew his dagger and strode forward.

Piers stood a few feet from the gate, his fists bunched, his eyes still accusing Palomides. Mordred tried to push Iseult behind him, but she refused his offer of protection.

'You never beat me in a fight at home, brother,' she said, smiling.

'I haven't fought you since I was six.'

She laughed, even though they were unarmed, surrounded by two armies and the advancing Sir Tristan. 

'You're a good friend,' I heard Mordred say to Piers.

'You're nothing but trouble,' replied the farmer.

'Someone will compose something bloody great about this,' said Elia, joining the line of four ranged against the army of thousands.

Arthur came to Merlin's side. The king's stomach rumbled. 'Oh I did enjoy that, my old friend,' said the king to his sorcerer. 'Though I confess that my belly churns at the blood. When was the last time I saw bloodshed?' He rubbed a scar on his right hand. 'I'd like to get the pretty red-head back to Camelot and show her my chambers.'

'Shortly, Arthur,' said Merlin.

There was a scuffle by the gates. Sir Tristan approached Iseult and tried to caress her face, but Mordred put himself between the knight and his sister. It was no contest between Tristan and the unarmed young man. Tristan dealt Mordred a blow in the stomach that doubled him over – I couldn't tell if he'd stabbed Mordred from that distance – and then dealt the man of Erin a blow on the back of head that put him on the ground. The Cornish knight went for Iseult again, and she raised a fist to him, but before he could touch her he found himself held back by Queen Melody. The old woman had appeared from nowhere and grabbed his arm.

'You murdering shit,' snarled the old queen, and threw her fist at his face.

There was a cry from above. Sir Bersulus screamed 'The queen!' at the precise moment that Sir Tristan's gloved hand snapped round Melody's throat.

Above, King Mark and Sir Amant turned to Sir Bersulus. Amant drew his sword.

Below, Sir Tristan snarled: 'I've been looking forward to this,' and stabbed queen Melody in the stomach.

There was a great groan from the soldiers on the battlements, and laughter from the Sessite horde.

'Open the gate! The queen!' shouted Sir Bersulus, and I heard the heavy bars of the gates start to slide open. 'The king is unwell! He is relieved.'

Soldiers on both sides of the old knight turned to their king, their spears pointed not to protect Mark, but restrain him.

Tristan stabbed his stepmother again and again. Her blood spilled over stone.

The gates opened a crack. Petal and Hebes appeared, and grabbed at Aglinda and Alisander's body, pulling them back into the castle. Piers and Elia saw what was happening, and followed them.

On the battlements, Sir Amant drew his sword and went for Sir Bersulus. The two of them grappled.

Covered in his stepmother's blood, Sir Tristan let Melody's body fall to the ground and advanced on Iseult, who was trying to pull Mordred back to his feet. At precisely that moment, Amant managed to unbalance Sir Bersulus and push him over the battlements. The loyal old knight caught hold of the younger man's collar, and pulled him over too. The two men seemed to hang in the air for a moment, and then fell, fast and hard, between Tristan and Iseult. Bersulus' leg caught Tristan's shoulder, and the bloody murderer fell.

'Go!' shrieked Arthur to the Sessites and the British on either side of us. 'The gates are open! The gates! Take the castle!'

Cautiously at first, the British ran forward. Some of Tintagel's archers realised that Arthur had broken his truce with their king, and began to shoot from the walls.

Arthur's army crowded the gate, trying to open it wider. I could no longer see Mordred or Iseult through the crowd. I didn't know if they'd managed to get back into the castle, or if they'd been stamped down by the charge of Arthur's soldiers. The air was full of war cries and arrows.

Merlin tilted his head. 'Most amusing,' he said coldly. 'Now, Lord of the Lake, let us discover the whereabouts of pretty Lady Neave and my spear, shall we?' I was frozen, my eyes locked on the struggle between Arthur's armies and the men trying to hold the gates of Tintagel closed. But then I was turned against my will to face Merlin, so I could only hear what was happening behind me.

Merlin's hand crackled with red light. He held his fingers before my face and I felt pain.

Oh, I felt such pain. It was as great as that Palomides had experienced in Camelot. I felt as if my spine was being torn out by Merlin's magic.

When it was over, Merlin stroked his beard. 'Of course. Obvious, really. Arthur!'

'What is it?' said the king. I heard him behind me, hopping from one foot to the other. He was giddy with excitement.

'Fetch Excalibur, and come with me. I may need the sword for this.' Down on the plain behind Merlin, Arthur's army seethed up the ridge towards Tintagel. I heard a roar behind me. Sessite voices. I couldn't see, but I think they had managed to force open the gates.

'Do I have to go with you?' said Arthur, breathing fast. 'This is fun. I haven't seen a good battle in years.'

'Arthur,' said Merlin. 'I'll borrow Excalibur if you prefer.'

A few moments passed. I heard Arthur shrieking at men to get out of his way. When he appeared in my field of vision he had retrieved his blade. His hand rested firmly on the hilt of Excalibur in its scabbard.

'This way,' said Merlin. He took Arthur's arm, and together they walked towards the edge of the high shelf that dropped down to the plain fifty or a hundred feet below. I found myself dragged along behind them.

It seemed as if we were going to walk into thin air, but when Merlin put the end of his ram's skull staff over the edge it came down not on emptiness, but gravel. The hills, plains, rivers and lakes of Britain folded towards us, and in one step the noise of battle disappeared, the blue sky turned grey, and we were surrounded by a heavy mist. I felt a wave of pure, undefined magic in that vapour, magic spilling out from the core of the Earth onto the surface of the world.

We were somewhere else, hundreds of miles north of Cornwall. A place Queen Morgawse had described to me.

The battle was far behind us. My friends, alive and dead, were far, far away.

Merlin blew gently into the air, and the mist around us parted. Ahead was a huge cave. The thick mist spewed from its gaping maw.

We had come to the Cave of the Dragon.