The imposing remains of Sheriff Hutton Castle tower up to 100 feet above the lawn that nestles alongside the home of Dr Richard Howarth and his wife Jenny.

Hailed as one of the largest and finest romantic ruins still in private hands in the North of England, the castle, near York, is a scheduled ancient monument, a local landmark and a shrine for Richard III enthusiasts who have travelled from as far away as Japan and American to see it.

Now they will have the chance to own it. The castle, along with the couple's four-bedroom converted granary, an adjoining two-bed cottage, outbuildings and 11 acres of land is for sale for £1.5m.

It is only the second time in its 600-year history that the castle has been on the open market. The first was when Dr Howarth's grandfather bought it in 1940.

Back then the regal ruin was part of a dairy farm and its Great Courtyard was full of barns, silos and tractors with little attention paid to its incredible past.

It was built in 1408 by the Neville family and confiscated by the Crown in 1471 on the death of its most famous member Richard Neville, known as Warwick the Kingmaker.

The castle, which sits in the centre of Sheriff Hutton village, was then owned by eight monarchs and has several claims to fame.

It was a major seat of government and Earl Rivers, brother-in-law of Edward IV, was staying there when he translated into English the first book printed in England by William Caxton.

In 1471 Richard III, then Duke of Gloucester, was also based there as Lord of the North.

And it can lay claim to the Princes in the Tower.

Although Richard III was condemned as a wicked uncle who murdered his two nephews, one school of thought is he sent them to Sheriff Hutton for safety along with other members of the Plantagenet family and they were then killed by victorious Tudor Henry VII after the Battle of Bosworth.

The property was in royal hands until the early 17th century when it fell into the hands of the aristocratic Ingram family, who began to dismantle it. In 1919 the castle and farm was bought by its sitting tenant, who sold it to Dr Howarth's grandfather, a textile manufacturer from Huddersfield.

The castle, which includes a gatehouse, four corner towers and a dungeon, is home to bats, birds and a friendly ghost known as Nancy.

"She is thought to be servant girl and wears a hooded black cloak," says Dr Howarth.

"My father saw her several times walking across the courtyard, though we've never seen her.

"She once appeared in the old farmhouse. A guest who had got up in the night to go to the loo saw her and was so frightened she fell down the stairs."

When he inherited the farm from his father, Dr Howarth left his job as a senior fellow at the University of Bangor and moved back to his childhood home in 1995.

He and his wife converted the farm's cart sheds and granary into a home and made the castle courtyard into a lawn.

Although the castle isn't open to the public, the Howarths have shown interested groups round the site and it has been used to host everything from church fetes, to medieval fairs and plays. A room in one of the towers, whose walls are 10ft thick, has been used for family parties.

"I love it the castle. I can remember clambering all over it as a child. For me it was a magical adventure playground," says Dr Howarth. "It's incredibly atmospheric."

But the upkeep of the castle has been a concern for the Howarths, who managed to secure a £540,000 English Heritage grant to stabilise it.

Dr Howarth, 67, who is planning to downsize to smaller property, says: "It is stable and resilient, though bits do fall off it.

"My hope is that we find an eccentric buyer who loves history and has a lot of money to throw at the ruin.

"Leaving it is quite a wrench. It's been a privilege to own it."

Estate agent Tim Blenkin, of Blenkin and Co, adds: "This is a chance to buy a remarkable piece of English history."

For more details contact Blenkin and Co, Tel 01904 671672.