Rodents are on the increase, and so are our worst fears. Jim White sorts fact from fiction and, below, relates a tail of horror
1. You dirty rat. True. They live in sewers, feed in dustbins and are incontinent. They leave a trail of urine wherever they go, particularly where they have just eaten, for example on your kitchen surfaces. "They carry an amazing array of parasites," says Frank Wheeler, head keeper of small mammals at London Zoo. "Six species of fleas, lice, mice, tape worms. Plus they carry most diseases you can think of. And then some."

2. They are indestructible. Not true. Lawrence Berry, of Hackney council's pest-control unit in east London, reckons the Brodifacoum poison that his department uses is proving effective. But since rats can achieve immunity against most poisons within two generations, pest control departments have to be on their toes: two rat generations is roughly every six months. Pest controllers sometimes resort to more basic extermination methods. Most carry baseball bats. "If you've got a rat loose in your living room, you don't want to wait for poison to work," says Mr Berry. "So we'll go in there and bash them, basically." Though favoured in the country, dogs are not used in towns. "People probably wouldn't like it if you turned up with a Jack Russell, they'd make a right mess," he adds.

3. They climb into cots and eat babies. Brace yourselves: true. There are several recorded instances of rats nibbling at the fleshy extremities - lips, earlobes, eyelids - of babies. Sleeping adults have also been assaulted, but usually wake up with the pain and fight the rats off. Sleeping drunks are thus vulnerable.

4. They breed like rabbits. Not true. Compared to rats, rabbits are sexually abstemious. The female brown rat produces up to 12 babies a litter, has a litter every six weeks and lives for two years. That's more than 200 babies per female.

5. They come up out of the toilet. True. According to the pest control unit at Hackney council, swimming the U-bend is a popular method of breaking and entering houses. In times of infestation, keep the lid down. They rarely make an attempt if the seat is in use, however, so your biggest fear - of rat invasion up an unprotected area - is unlikely.

6. They tie themselves in knots. True. Called a Rat King, this is an unexplained phenomenon in which up to 100 rats will link tails in a ritual daisy chain circle. They then starve to death.

7. When cornered they go for the throat. Not true. Frank Wheeler says a rat's only instinct in extremis is to get away. Running between an assailant's legs is a quicker and more successful method of escape.

8. You don't know they are there. Not true. While many people can cheerfully and unknowingly co-exist with mice, rats make their presence known about the house. They are noisy eaters, leave enormous deposits, consume vast quantities of electric wiring and dig.

9. Rats have no useful purpose. Not true. They are major predators of pigeons, eating eggs, babies in nests, even, when given the opportunity, fully-grown birds. This is good news since in the chart of disease carriers, rats (with seven potentially life-threatening ailments) come a poor second to pigeons (with 37).

10. They can climb up walls, chew through steel, get into anything. Not true. Black rats (Rattus rattus) are climbers, but they are also virtually extinct in this country. Brown rats (Rattus Norvegicus) are ground rats. They can only climb walls if the surface is rough enough to give a toe- hold - one good reason to avoid pebble-dashing. Though not as nimble as mice, which can squeeze through a hole the size of a wedding ring, they crawl through cabling connections and particularly piping. "If you've got rats in your house, it's a relatively simple thing to work out how they got in," says Lawrence Berry. "And then block it up."

11. They are the most terrifying animals on earth. Not true. Although resourceful, they are not particularly vicious, nor prone to attacking humans. Professor Davey of Sussex University believes that the cause of rat phobia is largely based on historical association with the spread of disease. "In the Middle Ages rats had the potential to wipe out humanity because they were the prime vehicle for the spread of disease. Our fear of them is a rationalisation of the disgust effect. We attribute that fear to obvious features - teeth, the tail - yet we are far more likely to catch something from a rat than to be bitten by one."

12. You are never alone with a rat. True. Rats are sociable animals and tend to infest in groups.

13. Rats can group together and turn on predators. True. Cats can come off second best in encounters with larger rats, but Jack Russells will gleefully take on any number. "I've seen films of 20 Jack Russells being sent into a rat-infested chicken coop in the country and clearing it in minutes," says Lawrence Berry. "Brilliant." In fact rats have fewer wild predators in Britain than anywhere else.

14. In the event of nuclear holocaust, rats would inherit the earth. True. They were recorded as the first mammal to relocate back into Hiroshima after the bomb.

'The builder opened a cupboard and a rat the size of a cat scuttled out ...'

According to the Sun this week, Nicky Chandler, 32, of Warminster, Wiltshire, is so fond of rats she has 47 of them. "They love jumping in the bath with me and my husband," the paper reported her as saying. "Sometimes we even switch off the television and just look at them playing around."

Nothing personal, Nicky, but Dominic Sykes would probably think twice about an invitation to dinner at your place.

Dominic moved in to a newly converted hospital complex in Battersea, south London, about six months ago. After a couple of weeks he realised that he was not the only new arrival. He heard scrabbling noises behind his kitchen units; he found cereal boxes chewed up; he met his neighbour, who said that something had devoured an entire fruit bowl overnight. Then Dominic found droppings the size of raisins on his kitchen surfaces. A man came round, took one look and said: "You know the size of rat that must have done that?"

Dominic had just joined the growing number of Britons who are playing unwilling host to rats. According to figures released last week, there are now more rats than people in Britain: 60 million, a population increase of 10 per cent in 15 years.

"The pest control people laid poison, but the things seemed completely immune," says Dominic. "One day I got the builders to come in and have a look. They thought it was hilarious, clomping about my kitchen calling, 'Here, ratty, ratty'. Then one of them opened a cupboard and a rat the size of a cat ran across the floor, and they all nearly crapped themselves."

After about a month in his new abode, Dominic began to feel run down. He suffered from repeated bouts of nausea and diarrhoea and developed an eye infection. Wet sores the size of 50p pieces opened up on his face. His doctor reckoned he had caught something from his house guests.

"The blood tests said it wasn't Weil's disease," says Dominic. "He thought I had probably contracted something after I left the lid off the margarine one night. They licked at it and the next morning I was spreading infected saliva on my toast." A course of stiff antibiotics cured the illness, and some judicious concreting to fill in the gap round the waste-disposal pipe kept the rats out. But Dominic remains on his guard.

"The pest control people told me to put a brick on the toilet lid at night and not to leave my windows open," he says. "I sleep on the floor on a futon in an open-plan flat and if I hear a noise at night, I'm awake. Everywhere I go, I meet people with rat stories. Frankly, I think rats are taking over this city."

And there is only one thing Dominic Sykes can do: organise a house swap with Nicky Chandler.