The sun gleamed on the soaked grasses of the crag’s crest. Here we were high above the valley where the river wound like a bright snake between its green verges. Steam rose from the roofs of the King’s camp. Round the wooden hall and buildings the small skin tents clustered like toadstools, and men were no bigger than wood-lice crawling between them. It was a magnificent place, a true eagle’s eyrie. The King halted his mule in a grove of wind-bitten oaks and pointed forward under the bare boughs.

“Yesterday you could have seen the western wall from here.”

Beyond the grove was a narrow ridge, a natural hogsback or causeway, along which the workmen and their beasts had beaten a wide track. King’s Fort was a craggy tower of rock, approached on one side by the causeway, and with its other three sides falling steeply away in dizzy slopes and cliffs. Its top was a plateau perhaps a hundred by a hundred paces, and would once have been rough grass with outcropping rock and a few stunted trees and bushes. Now it was a morass of churned mud round the wreck of the ill-wished tower. On three sides the walls of this had risen almost to shoulder height; on the fourth side the wall, newly split, sagged out in a chaos of piled stones, some fallen and half buried in mud, others still precariously mortared to outcrops of the living rock. Heavy poles of pine wood had been driven in here and there and canvas laid across to shelter the work from the rain. Some of the poles had fallen flat, some were obviously newly splintered by the recent crack. On those which were whole the canvas hung flapping, or had stretched and split with the wet. Everything was sodden, and pools stood everywhere.

The workmen had left the site and were crowded to one side of the plateau, near the causeway. They were silent, with fear in their faces. I could see that the fear was not of the King’s anger at what had happened to the work, but at the force which they believed in and did not understand. There were guards at the entrance to the causeway. I knew that without them not one workman would have been left on the site.

The guards had crossed their spears, but when they recognised the King they drew them back. I looked up. “Vortigern, I cannot escape from you here unless I leap off the crag, and that would sprinkle my blood just where Maugan wants it. But neither can I see what is wrong with your foundations unless you loose me.”

He jerked his head, and one of my guards freed me. I walked forward. The mule followed, stepping delicately through the thick mud. The others came after. Maugan had pressed forward and was speaking urgently to the King. I caught words here and there: “Trickery . . . escape . . . now or never . . . blood . . .”