It was a warm Saturday evening and Nick and Pauline Koupparis left a door to their three-storey house open as they watched Britain's Got Talent on television. Shortly before 10pm, a curious fox padded into their home in Victoria Park, east London, and made its way upstairs, where their nine-month-old twins Lola and Isabella were asleep. The fox attacked the girls on their arms and faces. When Pauline heard the crying, she rushed upstairs. "I went into the room and I saw some blood on Isabella's cot," she said yesterday. "I thought she'd had a nosebleed. I put on the light and I saw a fox and it wasn't even scared of me, it just looked me straight in the eye."

As the children were treated in hospital, where they were in a serious but stable condition, the shocking story spread around the globe, triggering a new panic about urban foxes. Police told local residents they should keep their doors closed in hot weather for their own safety. Neighbours spoke of how foxes creep not merely into their gardens but into their kitchens and living rooms. A fox trap was set; one fox has already been killed.

"Something should be done about them. I would love to get them out of here. They're really a nuisance and a danger," said one neighbour, Michael Parra. "I think the foxes are getting bolder. They almost go up to you. I've got fearful myself. They've gone towards my dog too."

Everyone who lives in a major city seems to agree they see more foxes than ever and these creatures are becoming bolder. Are we overrun with a new breed of fearless urban fox? Are these scruffy-looking, bin-raiding, lawn-wrecking monsters developing different patterns of behaviour to their fluffier, warier country cousins? Are they becoming more aggressive? And if so, what should be done?

A native mammal with little to fear from anything much except man, Vulpes vulpes has long fascinated and repelled us, attracting all kinds of fairytales and anthropomorphisms, from Reynard the fox in the Canterbury Tales to Roald Dahl's Fantastic Mr Fox. Hunting foxes with horses and hounds was outlawed in England and Wales in 2005 and the only piece of animal welfare legislation mooted by the Conservatives is a bill to bring it back. It is well known that David Cameron has enjoyed days out with the hunt. It is less understood that hunters imported thousands of foxes from Europe to lowland areas in the 18th century to improve their sport.

Foxes moved into cities in the 1930s and for four decades, until the 1980s, local authorities shot and trapped foxes in London in an attempt to exterminate them. This failed. By the 1980s there were an estimated 33,000 adult foxes in urban areas. Scientists believe populations have not risen significantly since. The highest densities of foxes are now found in cities but the Veterinary Association for Wildlife Management believes urban foxes still account for only 14% of the total population.