They were still some two miles from Picenum when Balbus heard the sound of approaching horses. The convoy was passing through a small forest of pine trees whose sharp scent filled the cold air. An outcrop of rock a short distance ahead obscured the road beyond. Balbus instinctively recalled his days on the Danube where the enemy’s favourite trick was to trap Roman columns in similar confined settings. He reined in and threw his hand up.

‘Halt! Down packs!’

As the wagons rumbled to a standstill, the German auxiliaries hurriedly set down their marching yokes, laden with kit, on to the side of the road and closed ranks at the head and tail of the convoy. Balbus passed the reins into his left hand, ready to draw his sword, and glanced round into the shadows beneath the trees on either side. Nothing moved. The sound of hoofbeats grew louder, echoing off the hard surface of the paved road and the rocks. Then the first of the riders came into view round the bend, wearing the red cloak of an officer. His crested helmet hung from one of the saddle horns. Behind him rode another twenty men in the mud-spattered white cloaks of Praetorian Guard rankers.

Balbus puffed his cheeks and let out a sharp sigh of relief. ‘At ease!’

The auxiliaries lowered their shields and the shafts of their spears, and Balbus waited for the riders to approach. Their leader slowed his horse to a trot and then to a walk for the last fifty paces.

‘Tribune Balbus, sir?’

Balbus looked closely at the other officer. The face was familiar.

‘What is the correct challenge, Centurion?’ he demanded.

‘The grapes of Campania are ripe to pick, sir,’ the other man replied formally.

Balbus nodded at the phrase he was expecting to hear. ‘Very well. You were supposed to wait for us at Picenum, Centurion …’

‘Gaius Sinius, sir. Centurion of the Second Century, Eighth Cohort.’

‘Ah yes.’ Balbus vaguely recalled the name. ‘So, what are you doing out on the road?’

‘We reached Picenum yesterday, sir. Place was like a ghost town. Most of the people had gone to a nearby shrine for some local festival. I thought we would ride out and meet you, and your boys there.’ He gestured towards the German auxiliaries.

‘They’re not mine,’ Balbus growled.

‘Anyway, we saw you approaching the town, sir, and, well, here we are. Ready to escort the wagons back to Rome.’