Oh, and when we rose from the table at last, the night was far spent and the dawn, gleaming like red-gold on the eastern horizon, seemed not the beginning of a day only – no, it was nothing less than the inauguration of a magnificent Golden Age.

The first of the stoneworkers' tribe appeared three days later -eight or so men with huge ox-drawn wagons full of tools and provisions. They did not come to the Tor, but went straightaway to the site and occupied themselves with establishing their camp in the valley at the foot of the hill where the new shrine would be built.

Arthur, eager to see the work begun, rode out to greet them, and some of the Cymbrogi went with him. We watched as they went about their chores, and by day's end five large leather tents of the kind the Romans used to make occupied the little plain; five more were raised the next day. These, they said, were to house their fellows and families, who arrived in four days' time. The numbers at the site swelled to perhaps forty in all, though that included the children, who seemed always to be everywhere at once.

Over those first few days, I had ample opportunity to observe the masons as they went about the chores of ordering their camp. They were odd men: small of stature, with broad backs and tough, sinewy arms and short, thick, muscular legs. They were a hard-handed, ready-tempered crew, and loud with it -when they were not shouting at one another, they were singing to make the valley ring – much like seamen in their ways. I would be surprised if a single one of them had ever sat a horse or gripped a sword, much less thrown a spear.

The next days were given, with considerable pointed discussion, to the preparation of the site. The stonemen grumbled endlessly at how poorly the land had been cleared, and they complained about the chosen placement and the disgraceful paucity of suitable stone in the region. Nothing was good enough for them, and they spared no breath letting the whole realm know it.

'God's truth, Arthur,' muttered Cai, quickly tiring of their surly opinions, 'if complaints were stones, the shrine would be raised by now -'

'And a cathedral besides,' added Bedwyr tartly.

'Pack the lot of them back to Londinium and be done with it, I say,' put in Rhys. 'We were doing well enough before they came.'

But Arthur took the carping and complaining in his stride. 'They are hounds without a handler,' he said. 'When their chieftain arrives, he will bring them to heel.'

The chieftain he meant was a bandy-legged, bald man with a beard like a bearskin. His skin, blasted by years of toil in sun and rain and wind, was as thick as the leather of his tent and just as brown. His name was Gall, and he walked with a limp and chewed hazel twigs, which he kept in ready supply in a leather pouch at his side. Tough as an old stump, he had but to speak a single word and his men leapt to obey.

Arthur liked him instantly.

Once Gall and his small brown wife arrived, the complaining subsided to a tolerable level and the work began in earnest -despite the appalling stone and lamentable situation. Again we were favoured with occasions aplenty to observe them, for the Cymbrogi were put to work cutting trees to supply the timber they needed. I never imagined masons required so much wood for their curious craft.

'That which you would build in stone,' Gall informed us, 'you must build first in wood.'

Nor could I help noticing that Myrddin seized every opportunity to go alongside the master mason, questioning his every move and thought in order to learn all he could of the stoneworker's craft.

When we were not fetching logs to the site, we were occupied supplying water for their camp. Though the drought continued as the long, dry summer wound slowly to its close, the spring below the Tor remained as sweet and cool and plentiful as ever, unaffected by the lack of rain. We filled empty ale vats and trundled them back and forth to the stonemasons' camp using their oxen and wagons. Were we ever thanked for this singular service? Ha!

In the midst of this turmoil, a strange and unsettling event occurred which should have served as a warning to us all. It was a Sabbath day, when the monks perform their holy offices and many of the Christian folk in the realm come to the chapel to observe these services and worship with the clerics. The masons, as it happens, do no work whatsoever this one day in every seven, and so they were free to join in the worship, which they did – singing out the hymns and psalms with unrestrained vigour.

Arthur so enjoyed this display of religious fervour that he went along to observe the vespers in the evening, and then invited everyone – monks and masons together – to the Tor to sup with him in Avallach's hall. Thus, we were all there together and enjoying the mood of festive cheer when I felt a queer sensation course through the hall. Beginning at one end of the great room and sweeping through to the other, I could see it ripple through the crowd as it passed, and felt a fluttery queasiness in the pit of my stomach. This was instantly followed by a peculiar numbing tingle like that of a winter chill on cheeks and nose and fingertips.

The hall fell silent with the kind of queasy anticipation that follows a sudden change in the wind just before the storm breaks. Illumined by the subtly shifting radiance of torchlight and hearthglow, the entire company stood motionless and staring, some with mouths open as if to speak, some with bowls halfway to lips as if to drink. I saw Arthur and Gwenhwyvar, half turned towards the doorway with laughter still on their faces, but frozen now. In everyone's expression and demeanour were the fast-fading remnants of a last, interrupted happiness.

I looked again and saw the cause of this interruption: a few paces inside the doorway stood a young woman; tall and slender, her long hair a mass of fiery curls flowing over her shapely shoulders like glistening water, her willowy form clothed in a deep green robe over a hooded mantle of shining gold, she stood imperious and erect – a monarch receiving the homage of her people.

For a long, frozen moment, silence reigned in the hall; suspended between one breath and the next, no one moved or spoke. And then I heard footsteps outside the hall. The approach must have surprised her, for she turned her head towards the sound, and in that instant the hall sprang to life once more as if on command and Myrddin appeared in the doorway behind her.

She faced Myrddin, and he halted – stricken in mid-step. I saw the smile of welcome freeze even as the words of greeting died on his lips.

The green-robed lady moved swiftly to his side and laid her hand gently on his arm. Then she turned and, together, beaming their good pleasure, they crossed the threshold into the hall – for all the world a regal couple entering their marriage feast.

My amazement at Myrddin's curious behaviour was immediately swallowed by an even greater astonishment, for, as she drew nearer, I realized that this lady was the woman I myself had discovered wandering barefoot in the forest. It was she whose pursuit had almost killed Llenlleawg – and three more besides. Gone were the rags, gone the fearful expression; gone, too, the bare feet, dirty hands, and unkempt hair. She appeared in every way the very likeness of a queen, from the hem of her robe to her curled and henna'd hair.

I stood rooted in surprise, but the crowd surged forward, exclaiming all at once. Myrddin, with a single word, silenced the tumult. 'Peace!' he said, his voice filling the hall from hearthstone to rooftree. He stood with upraised hand and halted the commotion as quickly as it had begun.

Then, turning to the young woman, he said, 'So! You favour us with your presence once more. I would know who it is that we would welcome. Lady, I command you, tell me your name.'