The next morning they ate some biscuits and clambered stiffly onto the backs of their horses. The ponies were no longer required, and were set free to fend for themselves. To the south, several miles away, a thin haze of smoke lifted lazily into the clear sky, and below lay the dark shapes of huts in the bend of a stream. That was where the Druids had spent the night, Prasutagus told them. In the distance, a group of horsemen escorting a covered wagon was visible. It was still not clear to Cato how the four of them could take on a much larger party of Druids and still emerge from the fight victorious. Macro, for his part was frustrated by the way they could do no more than tail their enemy, passively hoping for a chance to attempt a rescue to present itself. And all the time the Druids drew closer to the impregnable earthworks of the Great Fortress.

The spring day wore on as Prasutagus led them along narrow tracks, all the while keeping the horsemen and their wagon in view, and closing the distance only when there was no risk of being spotted. It called for an exhausting degree of vigilance. By late afternoon they were still some way behind the enemy, but close enough to see that the wagon was protected by a score of mounted Druids in their distinctive black cloaks.

‘Bollocks!’ said Macro, squinting into the distance. ‘Twenty on three isn’t good odds.’

Prasutagus merely shrugged and urged his horse along an overgrown track winding up the side of a hill. The Druids were obscured for a moment behind a line of trees. The others trotted after him, until they stopped in an overgrown track just below the crest from where they could see the Druids below, still heading south-east. Macro was riding at the back, watching the column, when Cato suddenly reined in, causing Macro to yank on his reins savagely to avoid riding into the backside of Cato’s mount.

‘Oi! What the fuck are you playing at?’

But Cato ignored his centurion.

‘Bloody hell…’ he muttered in awe at the panorama stretching out before him.

As Macro eased his beast alongside, he too could see the vast expanse of multi-tiered earthworks rising up from the plain ahead of them. With a recently developed eye for ground, Cato took in the neatly overlapping ramps that defended the nearest gateway, and the well-placed redoubts from which any attacker would fall victim to enfilading volleys of arrows, spears and slingshot. On the highest tier of the hill fort a stout palisade ringed the enclosure. From end to end Cato estimated the hill fort must measure nearly half a mile. Below the fortress, the rolling wooded landscape was divided by a serenely meandering river.

‘We’ve had it,’ Macro said quietly. ‘Once the Druids get the general’s family safely inside that lot, nobody’ll be able to get to them.’