Merlin, still with the long knife that had killed Gawain in his hand, seemed dumbstruck by our coming. His look of relief had vanished and now I could not read his face at all, but Nimue was shrieking at us. She held up her left palm, the one with the scar that was the twin of the scar on my left palm. ‘Kill Arthur!’ she shouted at me. ‘Derfel! You are my sworn man! Kill him! We can’t stop now!’

A sword blade suddenly glittered by my beard. Galahad held it, and Galahad smiled gently at me. ‘Don’t move, my friend,’ he said. He knew the power of oaths. He knew, too, that I would not kill Arthur, but he was trying to spare me Nimue’s vengeance. ‘If Derfel moves,’ he called to Nimue, ‘I shall cut his throat.’

‘Cut it!’ she screamed. ‘This is a night for the death of kings’ sons!’

‘Not my son,’ Arthur said.

‘You are no King, Arthur ap Uther,’ Merlin spoke at last. ‘Did you think I would kill Gwydre?’

‘Then why is he here?’ Arthur asked. He had one arm around Gwydre, while the other held his reddened sword. ‘Why is he here?’ Arthur demanded again, more angrily.

For once Merlin had nothing to say and it was Nimue who answered. ‘He is here, Arthur ap Uther,’ she said with a sneer, ‘because the death of that miserable creature may not suffice.’ She pointed at Mardoc who was wriggling helplessly on the gallows. ‘He is the son of a King, but not the rightful heir.’

‘So Gwydre would have died?’ Arthur asked.

‘And come to life!’ Nimue said belligerently. She had to shout to be heard above the angry splintering noise of the fires. ‘Do you not know the power of the Cauldron? Place the dead in the bowl of Clyddno Eiddyn and the dead walk again, they breathe again, they live.’ She stalked towards Arthur, a madness in her one eye. ‘Give me the boy, Arthur.’

‘No.’ Arthur pulled Llamrei’s rein and the mare leapt away from Nimue. She turned on Merlin. ‘Kill him!’ she screamed, pointing at Mardoc. ‘We can try him at least. Kill him!’

‘No!’ I shouted.

‘Kill him!’ Nimue screeched, and then, when Merlin made no move, she ran towards the gallows. Merlin seemed unable to move, but then Arthur turned Llamrei again and headed Nimue off. He let his horse ram her so that she tumbled to the turf.

‘Let the child live,’ Arthur said to Merlin. Nimue was clawing at him, but he pushed her away and, when she came back, all teeth and hooked hands, he swung the sword close to her head and that threat calmed her.

Merlin moved the bright blade so that it was close to Mardoc’s throat. The Druid looked almost gentle, despite his blood-soaked sleeves and the long blade in his hand. ‘Do you think, Arthur ap Uther, that you can defeat the Saxons without the help of the Gods?’ he asked.