He never coaxed, but he persuaded; he never flattered, but he encouraged those around him to think the best of themselves. Uther, of course, he had a different way with. Still, he was never devious or dishonest. The Imperial blood ran true in his veins and it was not in him to disgrace it.

As I came to know Aurelius, I came to honour him and to love him. He was what our people needed. He would be a true High King to unite all kingdoms with his power, just as Uther would be the battlechief to lead them on the field of battle. Together they made a most formidable force. Although, there was never any doubt in my mind which one of the two was the wiser and stronger.

Uther simply did not have his brother's character. He was not to blame, perhaps, for this lack. Men of Aurelius' stamp are rare. It was merely Uther's poor luck to have Aurelius for a brother and to be forced to live his whole life in his brother's shadow. In consequence, I undertook never to compare one of them against the other, nor ever to praise Aurelius in Uther's hearing – nor out of it – without also praising Uther.

A small thing, you may think, but empires have foundered on less.

With the kingdoms of the west and the north behind Aurelius, the stiff-necked lords of Lloegres in the south were suddenly faced with an almost insurmountable obstacle to winning the High Kingship for themselves or one of their own. Most, seeing the prudence of capitulation – if not the wisdom of unity – fell in with the powerful west and north in their support of Aurelius.

For others, in whom the white-hot fires of ambition burned, and blinded, it was a challenge that could not be ignored. They would fight Aurelius for the throne and quench the fire once and for all in blood. Woefully, many a good man lost his life to an ally who, on another day, might have been fighting Jutes and Saecsens instead.

It was a painful purging, but necessary. Aurelius would be king of all, or king of none. There was no other way.

I rode with him, always by his side, upholding him in battle as Taliesin had done for Elphin in another day. I will say that they had need of my help through that long, difficult summer. Aurelius, so sure and forthright ordinarily, would at times misdoubt himself and grow discouraged. 'Nothing can be worth this, Merlin,' he would moan, and I would embolden him with heartening words.

Uther had no stomach for fighting allies, but he was a warrior, and had a warrior's soul; he could dare, and do, many things other men would shrink from. And this earned him a fearsome reputation in the land: Uther, it was soon whispered abroad, was Aurelius' wolfhound – a cold-hearted killer who would tear throat and heart out of any man at his master's slightest command.

He was not so much cold-hearted as he was loyal, and his loyalty – to his brother, to the High Kingship itself – knew no bounds. In this, Uther earned my respect; his steadfastness was sprung from love – a love both genuine and pure. There are not many men who love so selflessly as Uther loved Aurelius.

This flame-haired firebrand lavished no love on me, however. He distrusted me with the same unreasoning suspicion many so-called enlightened men adopt in the presence of someone or something they cannot comprehend. He tolerated me, yes. And in time he came to accept me and even to value my counsel. For he saw that I meant him no harm, and that I shared his love of Aurelius.

Well, we three were a sight to behold: riding here and there with our troops, most of whom were unmounted – there simply were not enough horses to go round; hungry all the time; tired and dirty and sore; wounded and sick. But we were tenacious. We had fastened on the High Kingship, like hounds on the scent of the stag, and we would not be put off.

One by one, the warbands of Lloegres fell to us. One by one, we added the fealty of southern lords to Aurelius' rule: Dunaut, lord of the belligerent Brigantes; Coledac, lord of the ancient Iceni and Catuvellauni; Morcant, lord of the industrious and independent Belgae; Gorlas, lord of the contentious Cornovii. Proud, arrogant-men, each and every one of them. But they all bowed the knee to Aurelius before it was through.

Then, in the last shining days of false summer, just before the autumn rain spread its dripping cloak over the land, we turned to face Hengist at last.

It was not the best of circumstances. We might have waited through the winter, nursing our strength, healing our wounds, biding our time until the next spring. We might even have paused to crown Aurelius properly. But the thought of suffering the Saecsen horde even one more season on British soil rankled with Aurelius. 'Let them crown me later,' Aurelius said, 'if there is anything left to crown.'

Besides, as Uther pointed out, it would only give Hengist time to amass more men for, certainly, more ships would come across the Narrow Sea with the spring floods. Also, there was no telling how long the lords of Lloegres would remain loyal; they might forget their promises in the long winter months ahead. Best to strike now and settle the matter once and for all.

That would have been my counsel in any case. Hengist had already grown stronger through the long summer. He had been joined by his brother Horsa, with six more shipfuls of warriors. They had encamped themselves along the eastern shores – called the Saecsen Shore even by the Romans, who had built fortresses to keep the warships from raiding the coast. Now the Saecsens owned these fortresses and the land around them – lands they had been given by Vortigern, and other lands and strongholds they had not been given.

We marched to the east, to the Saecsen Shore, to the very doors of the fortresses themselves if need be, for we were determined to carry the fight to Hengist come what may. We need not have worried whether the barbarian would meet us. They were eager for blood; indeed, it had been a thirsty summer for them.

Aurelius raised his standard, the Imperial Eagle, and pitched his tent beneath it on a hill overlooking a ford on the River Nene. Somewhere across the river, well hidden, Hengist's war host was waiting.

'This will suit our purpose,' declared Aurelius. 'The Eagle will not fly from this hill until all the Saecsens are driven into the sea!' With that he plunged his sword into the turf in front of his tent and he went in to rest.

For men who had existed on a steady diet of war all summer, there was a surprising air of excitement in the camp. Men talked earnestly to one another, they laughed readily and loudly, they went briskly and happily about their tasks in a mood of high anticipation.

The reason for this, I came to understand, was partly that they trusted Uther to lead them wisely. He had shown himself an inspired leader, a natural battlechief: quick, decisive, yet cool in the heat of the clash, a consummate horseman and skilled with spear and sword – in short, more than a match for any who drew blade against him.

But part of the reason for the high spirits was that at last we were meeting the real enemy. Tomorrow we would fight Saecsens – not subdue an ally. There would be a true foe arrayed on the field against us, not a would-be friend. And this thought lifted the spirits of the warriors.

As I was going to my tent, Uther stopped me on his way to meet with his battlechiefs. 'Lord Emrys,' he said, the light taunt always in his voice, 'a word.'

'Yes?'

'It would be well to have a song tonight. I am thinking the war host would fight the better tomorrow for a song to set the fire in their hearts.'

The men appeared in excellent fettle to me, and in any event there were two or three other harpers in the camp, for some of the other kings travelled with their bards, and these often sang for the men. All the same, I replied, 'It is a good idea. I will ask one of the harpers for you. Which would you like?'