An hour later they saw a dozen riders some way ahead. Half an hour after that there were other horsemen high on the hills behind them, watching the main force march along the bottom of the valley. One of Vindex’s scouts came back, clutching at his side. His tunic was dark with a spreading patch of blood, which oozed between his fingers as he pressed them against the wound. He had been one of a pair of men sent along the valley side to the left. The other warrior did not return.

Ferox and Crispinus reached the wounded man as Vindex and two others were lowering him to the ground.

‘Bastards with horses marked on their heads,’ Vindex told them, looking grim even by his standards. ‘Shouldn’t have happened, though. The lad he was with rushed after the first one he saw. He’s one of the new boys.’ He shook his head. ‘Brigus here went after him and three of the buggers jumped him.’

‘What does it mean?’ Crispinus asked.

Ferox was scanning the trees on either side. ‘That we need to be more careful. And that we are probably in for a fight.’

Vindex kept his scouts closer from then on, and let the Batavian horsemen leading the main force come close before he pressed on. More and more little groups of warriors on horseback and on foot moved on the heights above them. A rider came from Brocchus to say that there were others closing in behind them.

They pressed on, fighting a sense that the valley was about to close in over them. The land sloped down and a little brook meandered along, finding the easiest path downhill. They had to cross the water again and again, following a track used by cattle. Up ahead there was the blackened trunk of an oak tree, struck by lightning and long since hollowed out, yet still standing.

‘I see it,’ Ferox said when he saw Vindex turn round. Crispinus strained, shading his eyes against the pale glare from the clouds, but shook his head because he could not make it out, until they got closer. Then he blanched.

The severed head of the lost scout was nailed to the wood. Whoever had done it had used an army nail, one of the long heavy iron pieces used to fasten great beams of timber. They had also cut off the man’s genitals and stuffed them into his mouth. Above the head, impaled on another long nail, was a straw effigy of a man, dressed in a tunic with red wool for hair and grey to show a breastplate and helmet. There was something wrapped around one of its arms and tied into place.

‘Do not touch it!’ one of the Brigantes shouted as Ferox jumped down and walked towards the ghastly warnings. Vindex did not speak, but looked as worried.