Monstrous super-rats which are immune to poison are descending on Britain, an expert has warned.
As many as 300 million of rodents with the ability to chew through concrete and mental are thought to be living out of sight in the UK.
A rise in fast food since the start of lockdown as led to an explosion in rats breeding within walls, basements and attics of Britons' homes.
Pest control expert Ian Helands warned the vermin were "taking over".
The rodents are able to chew through concrete to get into homes
PA
"They're cunning and getting bolder and bolder," he said.
"Basically, if they want to get into your home, they will.
"There are more rats than ever and they are taking over. I have seen some the size of cats."
Steve Balmain, professor of ecology at the University of Greenwich, added: "I could easily imagine 200 to 300 million rats here."
He continued: "Rats need to gnaw as their teeth grow continuously and gnawing keeps them sharp.
"Rats can certainly gnaw through concrete and metal, most normally soft metals such as tin, aluminium, copper and lead, but I have seen gnaw marks on steel, various hard plastics such as waste pipes and terracotta pipes - as well as concrete walls."
Last December a new study found that over the past 20 years, rats have been slowly developing immunity to poison.
As many as 78 per cent of the rodents are thought to now have genes that mean they can tolerate anticoagulant rodenticides.
A rise in fast food has been blamed fro the problem
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The British Pest Control Association has warned that too many people attempting to deal with rat infestations themselves had likely made the problem worse.
It warned a failure to properly use over-the-counter repellents has led to rats growing bigger in size and strength rather than dying.
It said: "The trouble is that people who try to treat problems themselves are likely to be making the problem worse.
"The rodents have become resistant and, in some cases, immune to off-the-shelf poisons to the point where they're actually feeding off the toxic pellets, which means their size and strength is increasing."
