'Where's the enemy?' He was dazed.

'Across the river.'

'Where's the river?'

' That way!' I was losing my temper and wasting my breath. 'The way we came in,' I reminded him, but he was already too confused.

'So where are we going?'

'To introduce ourselves to the nice fellows of the Fourteenth Gemina.'

It was not a success. Still, I had come prepared for that.

For one thing, no job I ever undertook concluded itself that easily, and for another the XIV Gemina had never been nice.

The fortress headquarters were designed to overawe any wild tribesman who dared put his nose round the Praetorian Gate. They formed the main vista as we stared ahead, and tramping closer certainly awed us.

There was one administration block in the fort. The two legions currently in post took up their quarters on either side, but they shared this edifice, which represented the fort's permanence. It was massively constructed. The facade comprised heavily colonnaded stonework on either side of a magisterial triple gate that looked straight at us down the Via Praetoria. Dwarfed, we crept in through the left-hand arch to find ourselves facing a well-tramped parade-ground that occupied more land than the forum in most provincial towns. Luckily no one was parading at the time. My timid companion would have expired from shock.

'We can't go in here!'

'If anyone issues a challenge, keep your pearly teeth clamped together and let me talk. As a general rule, while we're inside the fort don't argue with anybody wearing a sword. And, Xanthus, do try not to look so much like a lost understudy from one of Nero's theatricals:'

Three sides of the square were taken up by storerooms and the quartermaster's offices. Opposite, stood the basilican hall, which provided a focus for the formalities of both legions. It was where we were going, so I set off straight across the parade-ground. By halfway, even I felt slightly exposed. It seemed to take us half an hour to reach the other side and I could sense enraged centurions breathing fire from all the overlooking offices. I realised how the lobster feels when the water in the cooking pot slowly starts heating up.

The Principia was enormous. It stretched the full width of the complex. Decoration was minimal; it achieved its effect through size. The central nave was forty feet wide, separated by gigantic columns from sombre aisles each half its width again. The columns supported an almighty roof whose weight it was best not to contemplate while standing underneath. On a rainy day a whole legion could be crushed in there like anchovy bones in fish pickle. The rest of the time this formidable hall stood empty and silent, guarding secrets and forming a bold tribute to the skill of the army's engineers.

Through the gloom we could see the commander's tribunal at one end. The main feature, directly opposite the entrance, was the legionary shrine.

I walked across. My boots rang on the paving. There was a lurking scent of ceremonial oil, recent not rancid. Behind a border of stone screens lay a fireproof vaulted chamber; it guarded that other religious sanctum, the underground strongbox room. Up here, in the unlocked part, they kept the portable altar for taking auguries. Around it the standards were spikily arranged.

The Fourteenth had grabbed the most prominent position for their display, their companion legion obligingly tucking itself up on one side. In the place of honour gleamed the Fourteenth's eagle and a portrait of the Emperor wreathed in purple cloth. By the dim light from remote clerestory windows high in the main hall, I could see on the centuries' standards more medals for acts of valour than I had ever seen assembled together. Predominantly honours from the Emperors Claudius and Nero, they must have been awarded for outstanding service in Britain. Naturally they also had bronze statues of their titular patrons, Mars and Victory. The other legion's standards were by contrast unadorned.

We had not come to make obeisance. I winked at the eagle who was guarding the naked set of standards. Then I wheeled Xanthus into the nearby offices. The secretariat occupied the most significant place, alongside the shrine. Since no one else wants to bother with accommodation problems, the clerks always control the fortress plan. They naturally allocate the most desirable roost to themselves.

A bald will clerk nodded us towards the lavish suite which the Fourteenth had commandeered. Things were peaceful. That could mean either the legion were a dozy, inefficient outfit, or that the day's business had already been stamped up and cleared away. Perhaps their legate was taking a siesta at his own house, and the camp prefect had a cold. Perhaps the tribunes had all snatched a day's hunting leave. I reserved judgement. So long as they were keeping full granaries, a careful weapons count and an up-to-date log of what went into the savings bank, Vespasian was not a man who would quibble at the Fourteenth maintaining an unrushed commissariat. His interest was in results.

In the biggest room, we found two of the legion's senior men.

One, who was a non-combatant, wore a red tunic but no body armour. On a nail hung his helmet, adorned with the two horns that gave him his title of Cornicularius: head of the commissariat. In my opinion, the little horns are the legions' joke to make their chief clerks look ridiculous. His companion was a different species. A centurion in full kit, including a complete set of nine phalerae, the chest medallions awarded for dedicated service. He was over sixty, and his air of ingrained contempt told me this was the Primipilus, the First Spear, leading centurion. This sought-after rank is held for three years, after which lies a gratuity equivalent to middle-class status, and a passport into plum civilian jobs. Some, and I guessed this was one of them, opt to repeat their first spear posting, thereby making themselves public menaces in the way they know best. Dying in harness in some godforsaken province is a first spear's idea of a good life.

This primipilus had a short, thick neck and looked as if his party trick was killing flies with a head-butt. He had broad shoulders and his torso hardly narrowed on the way to his belt, but none of what went on below the chest was paunch. His feet were small. He hardly moved while he was talking to us, but I guessed he would be nippy when he wanted to exert himself. I didn't like him. That was irrelevant. He didn't care for me, either; that was what would count.

The cornicularius was much less impressive physically. He had a turned-up nose and a small, bitter mouth. What he lacked in presence he made up in personal venom and his ability to express himself.

When we entered, these two were tearing shreds off a soldier who had committed some misdemeanour, like asking an innocent question. They were enjoying themselves, and were ready to humiliate their victim all afternoon unless someone who disgusted them even more turned up. Someone did: Xanthus and I.

They told the soldier to sheath himself in his own scabbard, or words to that effect. He slunk out past us gratefully.

The primipilus and cornicularius looked at us, glanced at each other, then stared back at us derisively while they waited for the fun to start.

'I don't believe this!' the primipilus marvelled.

'Who let this rabble in? Someone must have bopped the gate security on their heads!'

'Those slack bastards in the First!'

'Good afternoon,' I ventured from the doorway.

'Shove off, curly!' snarled the primipilus. 'And take your garland girl.'

In my business insults are the normal convention, so I rode out the squall. I could feel Xanthus throbbing indignantly, but if he expected me to defend him in this company he could think again. I moved further in, and dumped the basket containing the Emperor's gift. 'Name's Didius Falco.' It seemed wise to be formal. I flipped my imperial passport at the cornicularius, who lifted it between one finger and thumb as if it had been found in a sewer. He let a sneer play around his tight little mouth, then shoved my tag across his table for the primipilus to laugh at too.