For the first time in more than 100 years, Old Wardour House has a habitable kitchen. It comes much to the relief of Polly Hughes, who moved into the Wiltshire house that her husband inherited almost 10 years ago.

The couple now sit down to dinner with a spectacular view over the ruins of one of England’s most romantic buildings, medieval Old Wardour Castle.

It was not always so. Luke Hughes, 49, a bespoke furniture designer, has lived in the shadow of the castle since he was born. He used to practise his rock-climbing moves on the walls. But it took his wife to prompt him to extend the house and flood it with light, after they bought out other family members who shared the inheritance in 1997.

“I noticed how the lack of light had crept up on Luke’s family and they had become used to it,” says Polly, a financial director at her husband’s company.

“I wondered why it was so dark. Because of the house’s position in a valley with trees on the slopes, it has practically no sun on the ground floor from late November to January. Not only was the house dark in winter, but its main rooms faced away from the sun, so it was also perishingly cold.”

The solution, designed by architect Eric Parry, who has masterplanned the World Square outside St Martin-in-the-Fields in London, was to flatten a derelict lean-to and build a two-storey glass box.

There was already a long history of adapting buildings on the site to suit changing circumstances; however, gaining planning consent to extend the six-bed property was a long, drawn-out process. The presence of the castle, a scheduled ancient monument, meant that they had to have not only the approval of the local council planners but that of English Heritage, too.

It took two years and a summons to London, where Luke had to make a presentation to English Heritage to prove his deep understanding of the site. In his favour, he had already seen one transformation of the house as a child. It was a wreck when his mother and stepfather bought it in 1961, taking two years and the then large sum of £40,000 to make it habitable.

The extension is the first step in a series of discreet modifications the couple plan to integrate the house into its surroundings as well as adapting it to modern needs — and those of Helena, their nine-year-old daughter.

Despite its relatively modest size, the extension built against the ancient curtain wall of Old Wardour Castle totally reconfigures the house, creating a lantern-like effect that infuses the house with light. Stone piers, in the same material as the original house and castle, echo the historic walls, interacting with large panes of clear glass. Looking in one direction gives a magical glimpse of some sun-etched ornament on the castle; turning around reveals a space tuned to modern domestic needs.

The centrepiece of the room, a long table, is equally suitable for formal meals or those assorted piles of domestic papers, shopping and homework that family life generates.

The working area follows the pattern of the original house. Three of its four sides follow the lines of existing walls, although one of these has a narrow window, sliced like an arrow-slit into the stone. Its fourth side opens onto the larger, lighter dining area. In the original portions of the house, views of the garden are restricted by the shape of the windows, and access to it limited to doors in the front and back halls. But in the kitchen the views are more panoramic, and the glass walls open out, giving direct access to the garden. Above the kitchen, Parry has created a master bedroom suite.

The £200,000 bill for the extension would have been at least 60% higher if Luke had not carried out much of the work himself.

The new glass “wing” is the latest chapter in the long history of adapting buildings on the site. The first records show it was a hunting park before the “new” castle was built at the end of the 14th century, adapting the idea of a castle as a rural stronghold into a luxurious country home.

In the late 16th century, Robert Smythson, one of the leading architects of his day, notably working on Longleat, modernised the castle, only for it to be blown up during the Civil War to flush out occupying Parliamentary troops. When the property was restored to the Arundell family in the early 19th century, it became home to the estate bailiff.

The house may not have tennis courts, swimming pools and extensive outbuildings, but the arcadian idyll does now have underfloor heating.

Further plans include a “solarium”, or adding a glass wall to the southern wall of the library.

“It is a thrilling chance to update a 1,000-year-old tradition,” says Luke, referring both to the long history of habitation on the site and the age-old striving to live in a rural paradise. “It’s not grand or beautiful, but it is in a spectacularly beautiful setting.”

Country Houses Today by Jeremy Melvin is published by Wiley & Sons,£34.99; Luke Hughes & Company, 020 7404 5995, www.lukehughes.co.uk; Eric Parry Architects, 020 7608 9600, www.ericparryarchitects.co.uk

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