Hundreds of sheep are being put to work as landscape gardeners by an environmental group which is creating a wildlife haven in the Chiltern Hills.

English Nature wants to clear a patch of chalk grassland on Shirburn Hill, near Watlington, and has recruited 400 sheep to graze long grasses and bushes away.

The aim is to keep down scrub on the 50 hectare site so that wild flowers, birds, butterflies and insects can thrive.

Five years ago, the land was designated a site of special scientific interest because of its bio-diversity but the area has only been grazed by wild rabbits for the past 30 years.

This led to concerns that the varied wildlife was being crowded out by long grasses and bushes.

Now English Nature has liaised with the landowner, Beechwood Estates, and invested £16,500 on new fencing to secure the site for livestock.

And grazier Bob White, of nearby Christmas Common, has agreed to move his sheep in to chew the foliage back.

Heather Whetter, of English Nature, said: "He benefits, the estate gets its land managed, and we get our wildlife.

"This kind of project is needed across the whole Chiltern escarpment. The chalk grassland is not being grazed as it should be."

Shirburn Hill is now expected to support plants such as candytuft, rockrose and wild thyme, plus butterflies such as the Marbled White and Duke of Burgundy. Birds of prey spotted there include hobbies, red kites and buzzards.

Mr White said: "It is good to see the old management practices returning to the hill. It's hard work checking the sheep on the steep slopes, but they are doing a good job."

Beechwood Estates is run by the Earl of Macclesfield, of Shirburn Castle, and his brother, David Parker, of Model Farm, Shirburn.

Mr Parker described Shirburn Hill as a really unusual type of landscape with its own special type of wildlife.

He added: "Traditional management will conserve the patchwork of open grassland, scrub and woodland."

The land has been used for shooting in recent years. Unusually, on the top plateau where soils have been leached, acid conditions have allowed chalk-heath to establish with a characteristic carpet of heather plants.