The world's biggest owl is secretly and successfully breeding in England, conservationists have disclosed.
Eagle owl - welcome return or alien predator?
Knee-high to a human with a two-metre (6ft) wingspan, the eagle owl is returning after centuries of absence.
Ringing of chicks confirms that a pair of the birds has reared 23 offspring on the North York Moors since 1997.
The first footage of a family of wild eagle owls in this country will be shown on 16 November in "Natural World - Return of the Eagle Owl" on BBC Two.
The owls are thought to have arrived from continental Europe, but the programme reveals there is controversy over their future here as they continue to spread.
Some experts and conservation organisations say eagle owls are an alien species that could prey on existing rare wildlife.
In areas where there are shortages of smaller mammals, the eagle owl will sometimes prey on larger ones, including other birds of prey.
It is even said to be capable of carrying off cats and small dogs.
Roy Dennis, a specialist in raptor conservation who has dedicated his life to bringing birds of prey like ospreys and red kites back from the brink of extinction, is convinced that the secretive eagle owl was once a British bird hunted to extinction.
He believes it should now be welcomed back as a necessary part of our ecosystem.
"There is no doubt that this bird could live in our countryside," he said.
"It's no different from Holland, southern Sweden or Germany [existing eagle owl habitats] and it's fantastic that we can now hear that call again in the countryside."
Programme producer Fergus Beeley, of Spider Movies, said: "Like it or not, eagle owls are here and more are bound to arrive as numbers grow in Europe.
"As predators of predators they may take some of our more familiar wildlife, but perhaps that's a small price to pay for sharing our land with such a magnificent wild creature."