Tony King is not an obvious killer. Cheerful and chatty, he drives around London in a van emblazoned with a larger-than-life (and dare I say younger-than-life) picture of himself, arms folded, grinning widely. He listens to classical music as he drives; it keeps stress at bay in the capital’s traffic, he says.

When his phone goes off, it plays Debussy’s Clair de Lune. There is a lot of Clair de Lune: these are busy times. On the van’s exterior, surrounding big, smiley King, are grey silhouettes of some of his victims, including a wasp, a rodent and a cockroach. There is also a wide-bodied insect that looks as if it could be from millions of years ago, but is very much current: a bedbug. There is another clue to the nature of King’s job in the company’s name: The Pied Piper. It may encourage his clients to pay up, if they remember the story.

It is boom time in the world of pest control. You will have heard about the bedbugs, even if you are lucky enough not to have experienced them first-hand. Plagues of rats and mice are rampaging through many of England’s older hospitals, with some NHS trusts having to call in exterminators almost daily. Rentokil, the best known name in the sector, says the number of inquiries related to bedbugs in the UK rose by almost one-third between January and September; in July, it reported a 65% year-on-year increase in infestations in the UK.

King started out at Rentokil 35 years ago, at 19, before setting up on his own a couple of years later. He has five technicians and the same number of vans. I am tagging along for a few days to find out why he has never been busier.

Our first job is a mouse problem at a recording studio in Hackney, east London, not far from where King is based. The back of the van is packed full of poisons, sprays, gels and traps. He slings his anti-rodent weaponry into a bag: pastes, grass seed, purple grain, Quorn … wait, Quorn? “Yeah, these are hipster mice. We also do gluten-free – no, Sam, corn!”

I am not going to dwell on the recording studio, as we do a few mouse jobs and this is not the worst. The problem is mainly in the kitchen – where the food is. There are lots of droppings, especially under the kitchen units and behind the fridge (the mice like the warmth). King leaves bait boxes containing poison – an anticoagulant similar to warfarin – and will return in a couple of weeks to check on them.

He finds the work satisfying: “You go to a job and it’s absolutely alive – rats or mice or bedbugs. You come back in a couple of weeks and there’s loads of dead ones; you’re picking up carcasses or you see the bait boxes are empty and you think: ‘Yeah, we’ve had a good result and the people are happy.’”

He is a people person – and he gets to meet all sorts of them: billionaires, drug addicts, sex workers, famous football managers, hoarders, a royal family (not the British one). He goes to all sorts of places: private and council homes, restaurants, businesses, offices, a mortuary. “Everyone gets pests,” King says.

There is still a smidgen of stigma attached to the business of pests. King gets clients asking if his van is branded (oh yes!) or if he can park round the corner, but it is getting rarer: “People are worried less about what the neighbours think, more about getting rid of what they’ve got.” He thinks pest control TV documentaries have helped.

Our second job is another mice one, in a fifth-floor flat. This is a third visit, so they should be gone. Sure enough, the woman who lives there hasn’t seen any – in fact, no one has since her mum saw a mouse in August. The bait King put down hasn’t been touched. Nor has her own trap, with bits of cheese. “You’ve been watching too many cartoons,” says King. Peanut butter (smooth or crunchy) is much better to lure mice.

King gets a lot of false alarms. He has stories of mice and rats that turn out to be noisy airlocks or even just water in the pipes. He gets cases of a kind of delusional parasitosis, too, where people imagine they are overrun with bugs. “What we say to those people is: we have to see something live; can you video it? Inevitably, they never do, because there isn’t anything. Or we say: can you collect some samples? We send them off to be identified and 99 times out of 100 they come back as household debris.”

There is nothing imaginary about the bedbugs. King says there is definitely widespread infestation in London – and they are not all coming over on the Eurostar. Numbers were increasing before anyone had heard about the crisis in Paris. He thinks an increase in travel since the pandemic began to ease has been a factor, but the situation in Paris, one of the top tourism destinations in Europe, certainly isn’t helping. “If you’re packing and you’ve got your suitcase next to your bed on holiday, that’s an easy way to bring them in.”

There are other reasons. James Logan, a professor of medical entomology at the London School of Hygiene and Tropical Medicine, says that an increasing resistance to insecticide is a contributing factor. The climate crisis probably is, too – insects breed better in warmer temperatures.

King points to council cuts, the disbanding of pest control teams and the use of outside contractors who have to tender for the work. “They screw right down on the price and don’t do the best treatments,” he says. Some councils offer reduced rates, but housing associations don’t always pay for treatments.

Individuals are feeling the pinch, too, of course. More people are buying secondhand furniture, or picking up mattresses that have been left on the street. But a three‑visit bedbug treatment from The Pied Piper starts at £300.

***

Our first bedbug job is a flat in Tower Hamlets, in a mixed block of private and social housing. King recognises the building; he has dealt with a moth infestation here. The woman who made the callout caught an unidentified bug running across the back of her sofa. She squashed it and put it in a piece of tissue. King unwraps it carefully. There it is, a bit flat, but unmistakably the same shape as the silhouette on the van. Positive identification: a bedbug.

King knows bedbugs don’t tend to come in ones. He also knows where this one came from. The woman’s son is staying with her, on the sofa, because his own flat is – guess what – infested with bedbugs. His house is council-owned and it has been treated, “but they’re probably using diluted spray, because of cutbacks and everything”, says the son. “I got bitten to madness; I’ve still got the scars.”

He thinks the one his mum caught was a lone soldier, but she is not taking any chances; they have bagged up all their clothes and belongings ready for King’s visit. He can’t see any more on the sofa, or the mattress, but that doesn’t mean they are not here. Just one more thing before he starts spraying – son and mum, plus their two dogs, have to leave for four hours. “You’ve come and messed up our world today, you know that,” the woman tells him. She turns to me: “Tell people it’s not good for their mental health.”

When they have gone, King gets his gear on: a white hazmat-type plastic suit, gloves and a mask, more Walter White, or CSI, than Pied Piper. He sprays insecticide over the sofa – and underneath, too. Likewise the bed and the corners of the room; anywhere they might be lurking. He will be back twice more to complete the treatment. King’s scary bedbug fact: although they like to feed regularly on human blood, they can live for months – up to a year – without feeding.

King thinks that, were it not for the situation in Paris, he might not have been called out for that job: “But the panic has set in; everyone is worried about it. I’ve got friends ringing up asking if they should be worried, a driving instructor asking if he should be spraying his car.” (They did do that once, spray a car.)

Mice, or possibly rats, have been reported on the fire staircase of the same building, so we go out that way. There are takeaway containers and other rubbish all over the place, which will be the reason they are here, King says. He will come back with bait and traps.

That adage about how you are never more than 6ft (1.8 metres) from a rat in London – is there any truth in it? “How far are we away from that?” he says, indicating an overflowing bin. Probably about six feet. But no, that one probably is more urban myth than fact, he says. They have always been in the city, though, and always will be, so there will always be work for a pest controller. He thinks he is safe from AI, too: “You have to have that experience to make decisions. AI will be able to give you guidance, but it won’t be able to take over.”

On our next job, at a rental flat in Leyton, another myth is cruelly dispatched – the one about cockroaches being capable of surviving a nuclear bomb. “Well, our insecticides kill them, so probably not,” says King.

He needs plenty of insecticide here. A trap – an adhesive tray containing a pheromone to attract the cockroaches – left on the previous visit is absolutely covered. Smaller than I imagined they would be, these are German cockroaches (Blattella germanica), although the species probably originated in south-east Asia. In Germany, they call them Russian cockroaches. It seems to be the same with pests as it is with everything else: blame it on foreigners, especially those with whom you have a difficult past.

On the tray, King points out the adults, male and female, adolescents and egg cases (“there’ll be 30-odd baby nymphs in there”). He has become interested in their life cycles. German cockroaches are the fastest-breeding species, he says, then shows me the evidence: when he pulls the fridge out, it is heaving. Cockroaches are running all over the floor, up the back of the fridge, into its workings; even the rubber seal around the door is full of them. When King unscrews the top of the washing machine, cockroaches pour out.

You often find cockroaches in restaurants and places where people live closely together. They eat anything, including each other, which helps King. He uses a gel to capitalise on “what’s called the domino effect. A cockroach eats the gel and dies; another will come along and eat that cockroach and he’ll die. It works up to 44 times.” Lovely.

Our next jobs are both bedbug-related. The first client is a woman in a flat in Shepherd’s Bush. She shows us the bites all up her arms. She went to her GP, who said it was bedbugs, so the housing association has replaced the mattress. That won’t solve it, says King – the bedbugs could be in the bed frame and the carpet. In fact, dragging the old mattresses out might have helped spread them through the building. He can’t find anything on the new mattress, or anywhere else, but, again, that doesn’t mean they are not here. So, on go the suit and the mask and out comes the sprayer.

The next flat is in King’s Cross. The tenant is from Afghanistan and speaks almost no English, but, judging by the unpacked case in the room, he hasn’t been here long. King lifts the seam along the edge of the mattress and shines in his torch. There is one – and another. He turns over the mattress and there are more, plus dark marks – the dreaded faecal marks. One makes a dash for it. I don’t know how the tenant got here, but it is hard not to feel very sorry for him. But, as infestations go, this is fairly light, King says. Really? He shows me pictures of a recent job. There are more bugs than mattress.

***

It is another day and we are in another part of town: Willesden, in the north-west of the city. “These Victorian houses are ideal for mice, because there are holes everywhere. Over the years, more gaps open up,” says King, pointing to a cluttered cupboard under the stairs. Then there is all the space under the floorboards. When you have a messy family living there, too, it is mouse paradise.

I know this because we are in my house. This wasn’t the plan, but, since King had a job two streets away, I thought we should stop in. I knew we had them; we had seen them, heard them, hoovered up their droppings. They had even eaten my granola (these are Guardian mice, after all). “There’s no shame; everyone experiences it,” says King. “The first step is admitting you have a problem.” My name is Sam and I have a mouse problem.

It is not a really bad infestation, though, I tell King. “It’s really, really bad,” he says, shining his torch into a crack. There are droppings everywhere, smear marks … “Smear marks?” I ask. “Mice have oily skin. When they go over something on a regular basis, it goes grey.”

He finds traces of them upstairs, too: in the bath panel, in the cupboards, in the loft. We are overrun. He lends me a motion-activated camera to put in our mousiest place, the kitchen. It is going to be like Planet Earth III, the domestic version. Later, I will question whether this was a good idea, on the first night the camera is triggered. Aww! Look at those ears and whiskers. It’s basically Jerry.

What if I said I didn’t want them to be killed? “People do ask if there’s a humane way of doing it – and there isn’t, really,” says King. “Mice don’t like going into traps; they’re really cautious about going into new things.” I remind myself of the droppings, the smear marks and – most of all – my granola. You know what, OK, they are pests, kill them. King makes up boxes with three different kinds of bait – paste, wheatgerm and grass seed – all laced with the anticoagulant brodifacoum.

His phone goes – Clair de Lune alert! He needs to go: to an older man in Shoreditch with cockroaches; to a pigeon problem in Islington (they don’t get killed – King uses something called fire gel that looks like flames to birds, so they stay away); to an invasion of mice at a West End theatre (no, not the one showing The Mousetrap). And, of course, to bedbug infestations all over town. Sleep tight …