This was a modest town house. Its provincial decorator had tried hard, but had been stuck with painting frescos of what he knew. Jason discovered the Golden Fleece beneath a holly-bush in a thunderstorm. Battle scenes rolled darkly below a frieze that only came to life when crossed by a skein of Rhineland wild geese. Venus, in the local Ubian costume of high-necked dress and wimple, was wooed by Mars in a Celtic felt coat. She looked like a market-trader, and he seemed a shy, rather paunchy chap.

The servant took me to a reception room. I was met by bright colours and gigantic couches with hugely padded cushions where a tired man could flop and forget his troubles. The reds were too earthy, the stripes too broad, the tassels far too fat. The total effect was reassuringly vulgar. The men who came here relied on strong-minded wives for taste, and they probably never noticed interior-design effects. They required somewhere clean and comfortable pervaded by scents of beeswax polish and gently stewing broth, somewhere which held basic recollections of their childhoods, in Italy. It was the kind of house where the bread would be served in roughly chopped hunks that tasted like ambrosia infused with hazelnuts. The music would be dreadful, but people would be laughing and talking so loudly they would not care:

I found Claudia Sacrata seated in a long chair, as if she was expecting visitors. She was no ravishing seductress, but a dumpy, middle-aged woman whose bosom was trussed so firmly it might have acted as a serving tray. Her grooming was careful. She wore a Roman dress in oatmeal and ochre, with fastidiously folded pleats on her shoulders where her stole was pinned with a large Indian ruby brooch that blazed Present from a Man! In appearance she reminded me of a slightly old-fashioned, good-hearted aunt tricked out to make a show in front of the neighbours at a Floralia parade.

'Come in, dear. What can I do for you?' The question could have been simple politeness: or a commercial bid.

I played everything straight. 'My name is Marcus Didius Falco; I am a government agent. I should be grateful if you would answer a few questions.'

'Certainly.' Of course, it didn't guarantee she would answer them truthfully.

'Thank you. I hope you don't mind if I start with you? You are Claudia Sacrata, and you keep a welcoming house. Do you live with your mother?' We both understood this euphemistic phrase.

'My sister,' she corrected. It was the same flimsy veil of respectability, though I noticed no chaperone ever appeared at our interview.

I plunged straight in: 'I believe you once shared the confidence of His Excellency Cerialis?'

'That's right, dear.' She was the type who liked to catch people out by admitting the unthinkable. Her shrewd eyes watched me while she tried to deduce what I wanted.

'I need to acquire some sensitive information, and it's difficult finding people I can trust.'

'Did my general send you?'

'No. This is nothing to do with him.'

The atmosphere changed. She knew I was investigating someone; if it had been His Excellency, she had intended to slap me down. Now she saw her most notable client was in the clear; her tone became proprietary. 'I don't mind talking about Cerialis.' She gestured me to a couch. 'Make yourself more at home:' Home was never like this.

She rang a bell for a servant, a nippy lad who seemed to have answered quite a few bells in his time. After surveying me coyly, she gushed, 'A hot-spiced-wine man, I should say!' Outside my own home I hate the stuff. To encourage good relations, I agreed to be a man who drank hot spiced wine.

It was a rich liquor, served in magnificent cups, with the spices rather overdone. A consoling warmth flooded my stomach, then seeped into my nervous system making me feel happy and safe, even when Claudia Sacrata cooed 'Tell me all about it!', which was supposed to be my line.

'No, you tell me,' I smiled, implying that women who knew what they were doing had tried to undermine me before. 'We were discussing Petilius Cerialis.'

'A very pleasant gentleman.'

'Bit of a reputation as a hothead?'

'In what way?' she simpered.

'The military way, for instance.'

'Why do you think that?'

This was a silly dance. However, I deduced that if I wanted information, talking about her precious Cerialis was the price I had to pay. 'I've been reading about his battle at Augusta Treverorum, for one thing.' I was sipping my hefty winecup as demurely as I could. If Cerialis wore his epaulettes in the usual style, he had bored everybody silly with the story of his big fight.

Claudia Sacrata posed and considered. 'People did say at the time that he made mistakes.'

'Well, you can look at it two ways,' I conceded, playing the friendly type. There was, in fact, only one way I could look at it. Petilius Cerialis had stupidly allowed his opponents to concentrate in large numbers while he had been awaiting reinforcements. That had been dangerous enough. His famous engagement was a shambles, too. Cerialis had built his camp on the opposite bank of the river from the town. The enemy arrived very early in the morning, crept up from several directions, and burst into the camp, throwing all into confusion.

'I understood,' Claudia defended him with solid loyalty, 'that it was only the general's brave action that saved the situation.' So that was his story.

'Undoubtedly.' My work demands a shameless ability to lie. 'Cerialis rushed from his bed without body armour, to discover that his camp was in turmoil, his cavalry were fleeing, and the bridgehead had been taken. He grabbed the fugitives, turned them round, retook the bridge with great personal courage, then forced his way into the Roman camp and rallied his men. He salvaged everything and finished the day by destroying the enemy's headquarters instead of losing his own.'

Claudia Sacrata wagged her finger. 'So why are you sceptical?'

Because the other assessment was that our troops had been led pathetically, the enemy should never have been able to get so close undetected, the camp had been inadequately guarded, the sentries were asleep, and their commander had absented himself. Only the fact that the tribesmen had been intent on grabbing plunder had averted complete disaster from our dashing general.

I restrained my bitterness. 'Why was the general not sleeping in the camp that night?'

The lady responded calmly. 'That I can't say.'

'Did you know him at that point?'

'I met him later.' So even before their intrigue started, he had preferred the comforts of a private house.

'May I ask how your friendship came about?'

'Oh, he visited Colonia Agrippinensium.'

'Romantic story?' I grinned.

'Real life, dear.' I guessed she regarded selling sexual activity as no different from selling eggs.

'Tell me?'

'Why not? The general came to thank me for my part in undermining the enemy.'

'What had you done?' I imagined some brothel intrigue.

'Our city was looking for a way to re-establish its ties with Rome. The town councillors offered to hand over the wife and sister of Civilis, plus the daughter of one of the other chiefs, who had been kept here as securities. Then we tried something more useful. Civilis, still confident, was placing his hopes in his best forces, warriors from among the Chauci and Frisii, encamped not far from here. The men of our town invited them to a feast and plied them with lavish food and drink. Once they were all completely stupefied, they locked the doors and set fire to the hall.'

I tried not to display too much shock. 'A friendly Germanic custom?'

'It's not unknown.' The most chilling part was her matter-of-fact tone.

'So when Civilis learned that his crack troops had been burned alive, he fled north, and Petilius Cerialis rode gratefully into Colonia: But what was your part, Claudia?'