I had spent an hour wandering about, trying to get my bearings and make sense of the plan, before I was apprehended and asked to explain myself. So far, the site officials thought I was just a curious sightseer on a visit from Rome along with a lady of distinction who was staying in a house in town that belonged to the procurator of finance for Britain. They assumed I had brought the noble Helena Justina to see her uncle Gaius and aunt Aelia, pausing at their house in Noviomagus Regnensis to recover from our long journey before travelling on to Londinium.

The clerk of works found a moment to speak to me. I held back, getting the measure of him. He tried putting me off, saying he had to go to a project team meeting; he said he would Like to allow me to wander around, but building sites were dangerous, so a safety edict declared the works out of bounds to unescorted visitors. I was about to show him the governor's introduction. Depending on his reaction to my docket from Frontinus, either I would make him squirm by producing my pass from the Emperor as well- or I'd merely let him know it existed.

He was a lean, middleweight, furrowed man of obvious intelligence. Dark brown eyes darted everywhere. Every time he crossed from his site hut to collect a hot drink from the covered canteen, he was looking for loafers, for errors, for sneak-thieves with their crafty eyes on equipment and materials- and it he had been forewarned to expect the proverbial man from Rome, then he was looking out for me. He oozed competence. And his restrained behaviour meant that whether or not he knew I was being sent to investigate, he would cope well when I came clean. If he was as good as my secretariat briefing had said, he would welcome my presence. If he had been away from Italy too many years, and had grown complacent or actually corrupt, then I would have to watch my back. The reason clerks of works can afford politeness is that apart from the architect, they hold absolute power.

He was called away again, to answer some question about setting out. He gave me a nod, a gentle hint to leave. Not me. While he got stuck in with the surveyor around the gro ma I stood where he had left me (so he would not worry what I was up to) but I refused to go, like a crass lad who had no social graces. Someone else then engaged the clerk of works in conversation, as tends to happen, so I tried chatting to the surveyor while he waited to resume.

"It's a prestigious site."

"All right if you like it," he returned. Surveyors are unhappy men. Intelligent, shrewd characters, they all believe that were it not for them, disaster would devastate any new construction. They feel their importance is not taken seriously. On both counts they are quite correct.

"Big project?"

"Five-year rolling programme."

"Big enough to go adrift!" I made the mistake of grinning.

"Thanks for the confidence," he answered sourly. I should have known that a surveyor would take it as a personal slight. He seemed tense. Perhaps he just had an edgy nature. He gave me a terse "Excuse me '

Time to assert myself. I could have produced a note-tablet and written memos. That lacked subtlety. For official missions you need a certain air. I had it. I could cause anxiety just by strolling to the edge of a new wall's foundations, then watching what was going on among the labourers. (They were hand-bedding flints in concrete between a double row of piles. Well, a man and a boy were doing that, while four other men stood by and helped them by leaning thoughtfully on spades.)

As I parked myself with my thumbs in my belt, simply looking in silence, the surveyor smelt audit immediately. I was expecting his half hidden jerk of the head to warn his crony; the clerk of works reappeared at my side again, with narrowed eyes. "Anything else, sir?" I knew as well as he did that it pays to be courteous. But I started as I intended to continue and it was tough. "The name is Didius Falco. I did some work for Flavius Hilaris a few years back. There were cock-ups in the organisation of the silver mines. Now they've called me back again."

He remained non-committal. "To my site?"

"You hear me."

"I wasn't told."

"But you are not surprised."

"So what's your work here?"

"Whatever is needed." I made it clear there would be no messing.

He knew better than to resist. "You have authorisation?"

"From the top."

"Londinium?"

"Londinium and Rome."

That caused the right buzz of excitement. "We have a team meeting about to start- I'll introduce you to our project manager."

The project manager was bound to be an idiot. The clerk of works clearly thought so; to have no faith in the project manager was the formal specification for his job. The surveyor was laughing behind his hand too, I reckoned.

"Who leads your team?" It can vary between the disciples, particularly on schemes like bridges or aqueducts, with a high engineering content.

"The architect." The fellow I had seen earlier, being rude. No doubt he would soon be rude to me.

"Any hope that they issued you one who knows his stuff?"

The clerk of works was formal: "Pomponius has had many years of training and has worked on major schemes." He deliberately did not comment, And he buggered up the lot of them. The surveyor sniggered openly, however. When this surveyor started his career, he would have undergone serious training of his own; some sessions would have been taught by grizzled old rowd-geniuses who called their task Stopping the bloody architect mining the job.

I had gained a good impression of this pair. "You mean, Pomponius is the usual mixture of arrogance, sheer ignorance and fanciful ideas?" The clerk of works allowed himself a faint smile.

"He wears Egyptian faience shoulder brooches!" confirmed the surveyor dourly. He himself was the smartest professional on site: crisp grey hair, immaculate white tunic, polished belt and enviable boots.

He carried instruments in a neatly buckled, well-oiled satchel; I would happily grab it oft a second-hand stall, even though it had obviously seen a lot of wear.

The clerk of works decided he should lighten the atmosphere. "Watch out if Pomponius offers you a presentation. It has been known to last three days. The last VIP was carried out unconscious on a stretcher Pomponius had not even started to show him colour charts and paint samples."

I smiled. "Then don't introduce me formally. Just slide me in at the project meeting and I'll make myself known to him at a later stage. I mean, after I've seen just how stupid he is."

They grinned.

We set off towards some elderly wooden buildings, ancient military hutments that looked as if they dated back to the Claudian invasion. Now they were being used as site huts, but must be earmarked for demolition when the new scheme was complete.

The project meeting would normally have started before this, but had been delayed. Somebody had had an accident.

"Happens all the time," the surveyor gushed dismissively. Although we had been acting like friends up to that point, he was glossing over an issue.

"Who was it? Is he hurt?"

"Done for, unfortunately." I raised an eyebrow. The surveyor seemed tetchy and made no further comment.

"Who was it?" I repeated.

"Valla."

"What happened to him?"

"He was a roofer. What do you think happened? He fell off a roof."

"Better get along to the meeting," interrupted the clerk of works. "Do you have a clerk, Falco?"

We were now entering the old military hutment they were using as the project manager's office. I let the unspoken issue about the roofer fade away, at least temporarily. "No, I take my own notes. Issue of security." In fact I had never been able to afford secretarial help. "My assistants back me up when needed."

"Assistants!" The clerk of works looked startled. A man from Rome was bad enough. A man from Rome with reinforcements was really serious. "How many do you have?"