This is not the calculation of a barbarian mind,' remarked Myrddin. 'Someone who has fought with British kings is leading this war.'

Who could that be? Most of the nobility of Britain was either fighting alongside Arthur or supporting him. Only one was conspicuous by his absence: Lot. Could it be Lot? That made no sense: Lot had given us ships, and shipwrights. His own sons had taken service in the Duke's army. I glanced at Gwalchavad, who appeared just as concerned and angry as the rest of us. There was no guile in him, nor treachery that I could see. Blessed Jesu, I would stake my life on it!

So the mystery remained: who could it be?

'They will have taken Trath Gwryd,' said Arthur, upon dismissing the messenger to food and rest, 'and have laid siege to Caer Alclyd and to Caer Edyn. This they have done with stealth and silence. They have chosen their positions well: fortresses instead of fords – our mounted warriors are all but useless. And, except for Caer Edyn, they have the advantage.' Arthur paused, his blue eyes sweeping the assembly before him. 'If they succeed,' he continued, his voice low, 'all we have done till now is less than nothing. Britain will fail.'

He had spoken the cold heart of fear. Now he spoke the bright fire of hope. 'Yet they have not won. The battle remains to be fought. We are not beaten because they have outwitted us this once. He of the Strong Sure Hand will uphold us, brothers, for we fight for peace and freedom, which is ever his good pleasure.'

Arthur raised his hands like a priest giving benediction, and said, 'Go now to your tents, and to your prayers, for tomorrow we begin. And once we have begun we will not cease until the Day of Peace has dawned in all Britain.'

The others left, but Cai, Gwalchavad, Bors, Myrddin and I stayed, for the Duke wished to speak to us privately. 'Will" you drink with me, friends?' Arthur asked.

'Sooner ask if a pig would grunt,' said Bors, 'than ask if Cai would drink!'

'Sooner ask that pig to fly,' replied Cai, 'than ask Bors to pass the cup!'

We all laughed, and drew our chairs round Arthur's board. The steward brought in jars and cups and placed them at the Duke's right hand.

As soon as we had drunk a cup together, we fell to discussing what was foremost on our minds: tomorrow's battle.

'A few of those machines Myrddin made for us last year would aid us now,' said Bors. 'We could make some.'

'No time,' said Cai. He was thinking of Caer Edyn, and his father besieged there. 'We must assault the walls.'

'You would brave those Picti arrows?'

'I am not afraid of their arrows.'

'You are welcome to them, then,' said Gwalchavad. 'In Orcady it is said: the Picti have only to see a bird to shoot it out of the sky.'

'Even the Picti cannot shoot what they cannot see,' put in Arthur.

'Then perhaps we should fight at night!' I said. Arthur smiled and slapped his knee.

All eyes turned to Myrddin, as a single thought gripped our minds. 'The moon will rise tonight,' he told us, 'but not until after the third watch.'

'We attack tonightl'

Never have I seen a sky so ablaze with stars, never so alive with light. Although the moon had not risen, the cloudless night seemed like bright midday to me. We all wore dark cloaks, and our faces were blackened with mud. We crawled over the cold rock on our stomachs, our swords hidden, our spearheads and shield bosses muddied. We hugged the ragged stone to our chests and climbed on elbows and knees towards the looming walls above.

Jesu preserve us, the Pied sentries regularly looked down over us! But their attention was occupied with the show of fire Arthur had contrived to conceal us: down in the camps men danced with torches and sang raucous songs. Their voices carried to the dun and urged us on.

Arthur, despite the objections of his chieftains, led the assault himself – up the cragged east side, well away from the narrow gate track. Once we reached the walls, one of us would go up and over to open the gate.

The one chosen for this was Llenlleawg. He volunteered almost before the words were out of Arthur's mouth, and the Duke was bound to let him do it or defame the Irishman by refusing. Since we had no reason to deny him – other than the fact we did not completely trust him – Arthur agreed. So Llenlleawg carried the braided rope and iron hook beneath his cloak.

After what seemed an age, we reached the perimeter of the wall. Huddled under cover of its shadowed roots, we waited.

I do not know how it happened: one moment I was looking down onto the firelit plain, and the next Pied arrows were whispering around me, striking the rocks and shattering their flint tips. I pressed myself flat against the wall, and others took what cover they could.

All at once I heard a shout. Out of the corner of my eye I saw someone stand. A rope snaked out and was pulled taut. The lone figure began to climb…

Llenlleawg! The mad Irishman was proceeding with the attack. Arrows flying, he had secured the hook and was climbing the wall… Jesu save him, he would be killed the instant he reached the top!

I expected next to see his pierced body plummet from the walltop to be dashed upon the rocks and, with him, our hopes of taking the fortress quickly.

But Llenlleawg somehow skittered up the sheer rock face and gained the top. A body fell – but it was not Llenlleawg's. I could tell it was a Pict, even in the darkness.

Somehow all this took place in silence – yet a more noise-battered silence I never want to hear! An entire age passed in the space of a few terror-fraught heartbeats.

Llenlleawg disappeared over the rim of the wall. And then…

Nothing.

A figure rose from the gloom beside me. Arthur's voice whispered urgently, 'Make for the gate! Go!'

I edged my way along the rough wall face, moving as quickly and quietly as possible. From the walltop above I heard not a sound – only the echoed shrieks rising from the camps. The dun was entered from the north by a single narrow door. I peered cautiously round the eastern corner and saw no sign of a guard above. I ran to the gate, reached it, and pressed my ear to the thick wood. I heard nothing from within.

I hunched down before the door and waited, signalling the others behind me to stay well back. An age passed, and another… I was about to go back to Arthur, when I heard a slight scratching noise on the other side of the door.

I pressed myself against the coarse wood. The scratching sound became a sharp rap, followed by another, and the muffled sound of someone cursing under his breath. It was Llenlleawg – the gate was stuck!

Seeking to help him, I pushed with all my might, and one of the warriors behind joined me and together we heaved our weight at the gate. But it would not budge.

'Get back!' came a hushed cry from the other side.

There came a whir in the air and the dull chunk of an arrow striking into the wooden planking of the door. Then another.

The Picti had found the Irishman! Our attack was discovered.

'Get back!' Llenlleawg called loudly – silence was no use to us now. 'You are pushing the wrong way!'

I stumbled back, and at once the door swung wide. The gate opened outward! How was I to know that?

I dived through the narrow opening, rolled on the stone flagging and came up with my sword in my hand. Warriors followed on my heels. Arrows whirred around our heads like bees, chunking into the wood or shattering against the stone and bursting into stinging fragments.

We swarmed into the yard and onto the walls. The Pied, newly roused and wakened, raised the alarm with their piercing battle wail as we hewed into them.

Suddenly, there was torchlight all around. More and more Picti were pouring into the yard. Their blue-stained bodies writhed in die dancing light, garish as nightmares. They rushed upon us with their long knives and double-headed axes. They howled in rage at our invasion.