I HAD BEEN an informer for over a decade when I finally learned what the job entailed.

There were no surprises. I knew how society viewed us: lowborn hangers-on, upstarts too impatient for honest careers, or corrupt nobles. The lowest grade was proudly occupied by me, Marcus Didius Falco, son of the utterly plebeian rogue Didius Favonius, heir to nothing and possessing only nobodies for ancestors. My most famous colleagues worked in the Senate and were themselves senators. In popular thought we were all parasites, bent on destroying respectable men.

I knew how it worked at street level – a hotch-potch of petty investigative jobs, all ill-paid and despised, a career that was often dangerous too. I was about to see the glorious truth of informing senatorial-style. In the late summer of the year that I returned with my family from my British trip, I worked with Paccius Africanus and Silius Italicus, two famous informers at the top of their trade; some of you may have heard of them. Legals. That is to say, these noble persons made criminal accusations, most of which were just about viable, argued without blatant lies and supported by some evidence, with a view to condemning fellow senators and then snatching huge proportions of their doomed colleagues' rich estates. The law, ever fair, makes decent compensation for selfless application to demeaning work. Justice has a price. In the informing community the price is at least twenty-five per cent; that is twenty-five per cent of all the condemned man's seaside villas, city property, farms, and other investment holdings. In abuse of office or treason cases, the Emperor may intervene; he can bestow a larger reward package, much larger sometimes. Since the minimum estate of a senator is a million sesterces – and that's poverty for the elite – this can be a nice number of town houses and olive groves.

All informers are said to be vile collaborators, currying favour, contributing to repression, profiteering, targeting victims, and working the courts for their personal advantage. Right or wrong, it was my job. It was all I knew – and I knew I was good at it. So, back in Rome, after half a year away, I had to stick a dagger down my boot and make myself available for hire.

It started simply enough. It was autumn. I was home. I had returned with my family, including my two young brothers-in-law, Camillus Aelianus and Camillus Justinus, a pair of patrician wild boys who were supposed to assist me in my work. Funds were not flush. Frontinus, the British governor, had paid us only rock bottom provincial rates for various audit and surveillance jobs, though we did secrete away a sweetener from a tribal king who liked the diplomatic way we had handled things. I was hoping for a second bonus from the Emperor but it would take a long time to filter through. And I had to keep quiet about the King's gift. Don't get me wrong. Vespasian owed me plenty. But I wanted to stay out of trouble. If the august one called my double bonus an accounting error, I would retract my invoice to him. Well, probably.

Six months was a long time to be out of the city. No clients remembered us. Our advertisements chalked on walls in the Forum had long since faded. We could expect no meaty new commissions for some time.

That was why, when I was asked to handle a minor documents job, I accepted. I don't generally act as someone else's courier, but we needed to show that Falco and Associates were active again. The prosecutor in a case in progress had an affidavit to be collected, fast, from a witness in Lanuvium. It was straightforward. The witness had to confirm that a certain loan had been repaid. I didn't even go myself. I hate Lanuvium. I sent Justinus. He obtained the signed statement without bother; since he was inexperienced in legal work, I myself took it to court.

On trial was a senator called Rubirius Metellus. The charge was abuse of office, a serious offence. The case had apparently been going on for weeks. I knew nothing about it, having been starved of Forum gossip. It was unclear what part the document we fetched had to play. I made the deposition, after which I suffered uncalled-for abuse from the filthy defence lawyer, who made out that as an informer from a plebeian district I was an unfit character witness. I bit back the retort that the Emperor had raised my status to equestrian; mentioning Vespasian seemed inappropriate and my middle-class rank would just cause more sneers. Luckily the judge was eager to adjourn for lunch; he commented rather wearily that I was only the messenger, then he told them to get on with it.

I had no interest in the trial and I wasn't going to stick around to be called irrelevant. Once my job there was finished, I left. The prosecutor never even spoke to me. He must have done a decent job, because not long afterwards I heard that Metellus had been convicted and that a large financial judgment had been made against him. Presumably he was quite well off- well, he had been until then. We joked that Falco and Associates should have asked for a higher fee.

Two weeks later Metellus was dead. Apparently it was suicide. In this situation his heirs would escape having to pay up, which no doubt suited them. It was hard luck on the prosecutor, but that was the risk he took.

He was Silius Italicus. Yes, I mentioned him. He was extremely well known, quite powerful – and suddenly for some reason he wanted to see me.

I DID NOT respond well to a haughty summons from a senator. However, I was now married to a senator's daughter. Helena Justina had become adept at ignoring stares as people wondered why ever she had anything to do with me. When she was not calmly ignoring stares, she had a scowl that could fuse brass locks. Sensing that I intended to be difficult about Silius Italicus, she began to frown at me. If I had been wearing a sword-belt, the fittings would have melted to my chest.

I was in fact wearing a light tunic and old sandals. I had washed but not shaved; I could not remember whether I had combed my curls. Acting casual was instinctive. So was defying orders from Silius Italicus. Helena's expression made me squirm a bit, though not much.

We were at breakfast in our house at the foot of the Aventine. This edifice had belonged to my father and was still being renovated to our taste. It was six months since any fresco painters had bothered to show up; their pigment odours had faded and the building had reverted to nature. It had the faint musty whiff that afflicts elderly homes which have suffered flooding in the past because they were built too close to the river (the Tiber was a mere twenty feet away). The building had mostly lain empty while we were in Britain – though I could tell Pa had been camping out here as if he still owned the place. He had stuffed the ground floor with pieces of hideous furniture that he claimed were in `temporary storage'. He knew we were back in Rome now, but was in no hurry to shift out his impedimenta. Why should he? He was an auctioneer and we had provided a free warehouse. I looked for anything worth pinching, but no reasonable customer would bid for this junk.

That didn't mean it would not be sold. Pa could convince a ninety year-old childless miser that he needed an antique cradle with its rattle-hook missing – and that the victim could afford to have its rockers renovated by a deadbeat carpenter to whom Pa just happened to owe a favour.

`I'll throw in this fine Alexandrian rattle,' my father would say magnanimously (forgetting to do so, of course).

Since we could not climb into our dining room until my parent removed half a huge stone corn grinder, we ate upstairs in the roof garden. This was four storeys away from the kitchen, so we dined on mainly cold buffets. For breakfast, that posed no problems. Ever bighearted, Pa had lent us a double-jointed Bithynian slave to carry up the trays. Bread rolls and honey survived, even when the sour-faced nonentity took his time. He was useless. Well, Pa would have held on to him, had he been any good.