Stuart Finesilver is a trained assassin. But most likely you will greet his appearance with relief for he will have come to rid you of unwanted guests.

For the past seven years, the 32-year-old pest control officer has been rooting out vermin in the north London borough of Barnet, in pursuit of "rats, mice, cockroaches, fleas, bedbugs, carpet beetle, and exotic ants".

"I was never squeamish," he said. "The only thing I have got a slight issue with is those big moths which make that horrible clunky noise when they bounce off your head - it goes right through me. Fortunately, you get that more on the street than doing this job."

A member of Southgate Progressive Synagogue, where his eight-year-old son Andrew goes to cheder, Mr Finesilver used to work as a technical surveyor for a large property company until he lost his job in the financial crash. In his previous work his arrival at a house might portend the unwelcome discovery of woodworm or damp.

But now, he said, "it's quite nice to knock on the door and have people pleased to see me."

He started out clearing "wasp's nests. My colleague showed me how to do it. He put on his hood and big gloves and squirts the wasps and they go crazy. I had never been stung before so I didn't know if I was going to react badly to a sting. I got stung for the first time a couple of years ago - which is unavoidable when you are in close proximity all the time - fortunately, there was no problem."

Much of his work is detection, locating the source of a problem such as a broken airbrick or a cracked drain cover, or tracing a rat trail - "their hair brushes the ground and it leaves a smooth patch of dirt."

He and his colleague, who work for Re - a joint venture between Capita and Barnet Council - go out on around 40 calls a week. In busy periods, at the height of the wasp season for example, they may work weekends as well. More recently, their beat has included the neighbouring borough of Enfield.

His most troublesome adversary are bedbugs: "They gross me out the most, if anything does. In the worst cases they can cause issues like anaemia because of the amount of blood they are drawing. They are worst because of the amount of work involved in having to clear them. You have to spray every little thing in the room. And wearing a full suit with a helmet on a hot day makes it the least pleasant."

Bedbugs, unfortunately, are on the increase. "We put a lot of that down to the recession - more people are renting, more short-term lets. You get more families living in one home and more re-use of secondhand furniture," Mr Finesilver explained.

But at least he has recorded no rise in rats. If you want to deter rats from your garden, he said, best to avoid bird-feeders, to pick up fallen fruit from trees, clear away undergrowth around sheds and generally try not to leave inviting places for nests.

Mostly, poison will do the trick with rats or mice. Occasionally, they will use traps, although, Mr Finesil
ver said, "there is always the risk you won't get a clean kill, no matter how carefully you set it. And we always try to make sure it is done humanely, to make sure they go in the most peaceful way."

Despite the classic cartoon image of mousetrap and cheese, he said, "I have never seen mice go for cheese. Most of the time, they go for sweeter things like peanut butter, chocolate spread, chocolate in general".

Sometimes he has literally had to take the law into his hands. "I had a phone call, 'there's a rat behind my fridge'. When I got there, I pulled out the fridge and there was the rat. It was quite scared." A natural reaction, especially considering he stands 6ft tall.

"I put down some sticky pads and flushed it out and it got caught in the pads. I then took it out and broke its neck in a quick, humane fashion - a blow to the back of the neck to sever the spinal column. It's not my favourite thing to do at all, but it's an essential part of the job, although not very common - maybe once or twice a year."

He used to keep rats as pets. "When I was a student, I had a hooded rat and his name was Ludo. Rats have an intelligence level about the same as dogs, but a domestic rat is very different from what you'd find in your garden. They are selectively bred for the traits that make them pets."

Mr Finesilver's household now includes a dog, cat and two goldfish, though no rats. But he had to take action to stop the cat presenting the family with offerings of live mice. "Through trial and error, I found bells on his collar made it a lot harder for him to catch anything."

Sometimes he is asked to identify a strange creature that has been accidentally transported here in a package from abroad. At a recent Pestex convention, he went to a session to learn about venomous spiders.

A spate of publicity about false widows, a spider with a poisonous bite which is actually native to Britain, led to an increase in call-outs last year.

"I've never seen a false widow apart from at the conference I went to learn about it. They wouldn't be in your house - they are the sort of thing you'd see on a signpost rather than running around your bathroom floor. Most of the time, it's just a normal garden spider and nothing to worry about."

But though he has escaped an encounter with a false widow, the job does have its hazards. "I quite often get bitten when dealing with fleas and unfortunately, every now and then, I have to make sure my house is treated as well - because nobody likes taking their work home with them, me less so than other people."