The Brits have inadvertently bred super rats:
Twenty-two inches from quivering whisker to fat tail, they can chomp through concrete and leap more than two feet in the air. Sauntering down your street in broad daylight, insolently raising two claws to the binman, they rifle through your rubbish and scoff poison as if it was milk chocolate. There is something of the night and also something of the urban myth about the nearly indestructible super rat coming to a pile of carelessly discarded foodstuffs near you. But Britain’s pest controllers are adamant: they are receiving more panicky reports of rodent infestation than ever, and it does seem that our rats are evolving into something not seen before.