Back in the mid-nineties, like a lot of people my age, I was short of money. What can I tell you? The rent needed to be paid, I always had an empty stomach, and I wanted a better car than the one my dad had given me. It might not sound like much of an excuse, but when you're worried about a roof over your head each and every day, your belly aches, and you're driving an L-reg Toyota Previa, your morals can change, and change quickly. And that's what happened to me.

I got into the game when I met a vet at a late-night members club. It had a 2am bar licence, which meant people like me, who couldn't drink enough during the day, would go down a set of grubby looking stairs into a basement, knock on a door, say a codeword, and get to drown those sorrows for another three, three and a half hours.

Four nights of the week, that's where you'd find me, nursing a watery whiskey and coke, listening to soft rock piped out a tiny, tinny set of wall-mounted speakers, with two or three similarly lonesome men dotted about the tiny, grim room. It was basic, at best - whitewashed walls, much too powerful bare light bulbs, a smell of fried food that wasn't ever offered to the clientele. It's one of those funny quirks you sometimes see, but most of the regulars looked to have some kind of eye injury - a milky pupil, or a jagged scar that keeps it half closed. I wondered if was near some kind of eye hospital, but never bothered finding out.

The only other point of interest in the room was a beat-up piano next to the bar, but no one ever so much as pressed a single key in all the time I was down there.

The vet came in one night in November, his white coat wet from the rain that had been falling in a fine mist since that morning. He went to the bar, ordered a drink, knocked it back in one go, ordered another. He glanced around the room, as if looking for someone, and our eyes met. He nodded, asking if he could join me. I shrugged. He came over. I thought he might be trying to pick me up. I'd set him right soon enough.

“Does anyone know you're here?” he said in hushed tones. I shook my head, but before I could reply, he reached into a small leather satchel and pulled out a photocopied A4 sheet, and pushed it towards me. “This is his picture.”

The photo was of a cat, with the name “Snuffles” written underneath in capitals. The thick, smudgy black ink of the photocopier made it look just like one of those “missing pet” posters that you rarely see these days.

“Chronic kidney failure and cat flu. If they'd have brought him in earlier, maybe I could have done something. But they didn't, so I can't.” He was staring at me, unblinking. “They seem like such a nice family, I didn't want to have to tell them there was nothing I could do for him. It would have broken their hearts. So - damn it!” He swallowed deeply. “So I told them he'd be fine, that he's got years left.” He bunched his hand into a fist, and struck his leg once, quite hard.

He looked up, his eyes welling. “And that's why I called you.”

The vet glanced nervously to the door as it opened, a young woman leading a smiling man with spiked hair in her wake. He settled back into his seat, spooked but holding it together. Just as I was about to tell him that I wasn't the man he presumed I was, he spoke again. “The money is in the envelope that I'm leaving on the chair. It's all there, there's no need to count it. Please, when you do it...” His voice broke, and he raised a hand to his nose to keep himself in check. “Please...make it quick, and make it clean. And may God have mercy on us both.”

With that, the vet rose, pulled his coat back on, and ducked through the door as it was swinging shut. Confused, I reached over for the envelope, feeling it was fat with notes. Holding it beneath the rim of the table, I counted, 10, 20, 25, 30, 35. Thirty-five pounds. Whatever the job was, it was worth a whole lot of money. And that was the kind of job I'd been looking for.

On the photocopy beneath the picture of Snuffles was an address - Harrow, a place I knew well. I'd briefly worked in the Nando's there, but gave it up when the fucking twat of a manager sacked me. It was a residential address. And beneath that, six more words in the same hand: “This is the cat to kill.”

Three days later, I was standing in a quiet suburban street of terraced houses. It was only the afternoon, but the winter dusk was approaching quickly, signalled by the cars starting to turn on their headlights as they drove past. The address for the house I'd been given was a nice enough looking place - through the downstairs window, I could see some children's drawings on a fridge, a couple of indistinct family photos above a fireplace, and dried pine cones scattered across the hearth.

I'd need to get round the back, that's the place where I'd most chance of not being seen. The air-rifle was heavy on my back. For the first time, I was starting to get light flutters of nervous anticipation in the pit of my stomach. I thought of the money, took a deep breath, and opened the wooden gate into the front garden.

To execute a professional kill on a cat, you have to get inside that cat's mind. You have to know him better than he knows himself. Where would you go if you were a cat? Who would you hang around with? Where would you go to unwind?

You might think, “Well, cats eat mice, I'll hang around with the mice, and sooner or later, the cat will turn up.” It isn't that easy, trust me. For one thing, it's impossible to hang around with mice. You might see one, but it'll run away almost instantly. The same with birds. They're impossible to hang about with. They just fly off, and take it from me, they don't come back.

What do cats like? String, sure. You go straight to the source, a factory that makes string, you have a look around. Any cats there? Not in my experience. Fishmongers? The same.

Why not try and get accepted by a group of other cats, see if you can't get close to your target that way? It just doesn't work. They run off when you get near them. Sometimes they'll look like they're going to stay, but then start flattening themselves to the ground, and start whipping their tail back and forth. You've got ten seconds of that before they tear off in the other direction, or stand their ground, hiss loudly, and then tear off in the other direction.

You'd think wearing a cat costume will get you closer? I can tell you it doesn't. The same thing as above happens, only you don't see it too well as the eyeholes are never quite even enough for both of your eyes.

After the first hit - which was a partial success, at best - the vet began turning up at the member's bar with more frequency. The first time he'd been furious, saying Snuffles had been brought into the surgery with a damaged leg, the family believing he must have been hit on the road outside. The vet agreed with them, but examining the leg, he thought the damage was more consistent with someone booting him really hard, and then running off. He'd not told the family about his suspicions.

I said I'd needed more time, that he'd proved to be a tricky customer, that he'd gone all floppy when I'd collapsed on top of him and managed to wriggle out in the frenzy through my thighs. He calmed down, saying thankfully, it had all worked out in the end - Snuffles had died in his basket a few days later, presumably of shock, and the family put it down to the car accident that never occurred.

I told him that's exactly what I'd intended.

No-one would be sought in connection with the death. I smirked at the vet. The perfect hit.

From that point on, I started noticing the member's club was more full than it had been before I'd met the vet. More men would turn up every night, clearly not drunk or drinkers, looking nervous and out of place. Sooner or later, each of them would wander over to my table, ask if they could sit down, and pass over an envelope and an A4 sheet of paper.

Not all of them were cats - many were rabbits, which one vet confided to me they find difficult to treat because they're very different to other animals. Nothing else is like a rabbit. They remember all the general stuff, but specifics - too much to remember. Plus, it's not like rabbits are expensive. People can always get another rabbit that isn't broken. Same goes for lizards, but they do cost more.

I never asked them why they came with their envelopes stuffed with as many as seven notes. One of them, a nervous young man with a perfect centre parting and thin spectacles, once told me why he'd come. It was breaking the news that nothing could be done to the children. To be the human face of a child's first tragedy, the first adult who breaks a child's heart completely and forever. He'd asked me to do a hamster with an abscess. It could have been treated, but he'd brought the thirty five quid, so who was I to tell him how to do his job?

I chucked it all in after one job went wrong. It was another cat, and somehow, as it was all going off, I lost an eye. The money wasn't enough after that.

I still drink in that member's bar, but these days, it's pretty quiet. The only thing that's changed is there's a new fella who comes in regular, sits at the back. He's been around for a few weeks now. Keeps himself to himself. I took his paper earlier. He's not good at the Sudoku.

This evening, wet and dark, a man in a white coat I'd not seen before came in. After he'd necked a shot, he nodded over at the new bloke. The new bloke didn't respond, just too kanother slug of his drink. The man at the bar ordered another, and picking it up, casually wandered over to the table. As he sat down, I could see he was holding a small envelope and a folded piece of A4.

I went back to my paper.