Desig House: An irresistible Georgian house in a flower-filled valley

Hidden in a Somerset valley, this centuries old house was an irresistible challenge for its owners, who put together a team including architect Ptolemy Dean for the painstaking restoration, which won a Georgian Group award in 2015

The great Icelandic volcanic ash cloud of 2010 disrupted many people's travel plans, but when designer Sophie Hale and her husband Roland decided to scrap a trip to Istanbul and settle for Cornwall instead, it precipitated a more permanent move in their lives. On the way, they viewed a property for sale hidden in the depths of the Somerset countryside, on the edge of the Blackmore Vale. At the bottom of a steep slope of ancient trees and flower-filled meadows lay Shanks House, so remote and undefiled in appearance, with its neat ashlar face, five bays and central pedimented doorcase, that it seemed like travelling back to an earlier age.

Of course, there was a bidding war for such a trophy, but decisiveness won through and so began the huge task of discovering what lay behind such a perfect façade. Ptolemy Dean Architects was commissioned to undertake the detective work and restore the house in a way that would reconcile English Heritage's strictures on Grade I-listed buildings with the comforts of twenty-first-century life. Planning and listed-building consents were sought in stages, supported by a wealth of historical research. Relations with English Heritage and South Somerset District Council were unusually amicable and constructive - Ptolemy talks enthusiastically about the collaborative process.

First to be tackled were extensive outbuildings not even on the plans when the place was sold. Once bat and newt experts had given the all-clear, self-contained accommodation was created for the family to live in during work on the main house. When shown photographic evidence from the 1870s, the planners conceded that the stable roof could be raised back to its original height and rethatched, making space for a gym, steam room and games room.

Even greater feats of deconstruction and reconstruction were required for Shanks House itself. Behind the symmetrical east front, a jumble of older buildings in soft, gold Cary stone is attached. Dating back to the 1560s, the property was sold in 1602 to the Watts family, who enlarged it over their century and a half of ownership. The east wing was added around 1750, but thereafter the house seems to have stood largely undisturbed, passing through successive generations of the Grant-Dalton family until it was sold in 1920 to their tenants.

Beneath a vast tented scaffolding structure, the builders, R Moulding & Co of Salisbury, removed, repaired or replaced rotten roof beams, floor joists and crumbling wattle and daub ceilings. Dormer windows were reintroduced on the bleak north front - again on the basis of old photos - and the whole re-rendered and painted a mellow cream. The happy discovery of a lintel allowed a garden door to be reintroduced into rooms that could be converted back to their original use as the kitchen. Most radically of all, the main entrance to the house was reorientated from the north to the west front.

Forensic care was also lavished on the interior framework. Stone flags taken up to install the underfloor heating were extended and new joinery blended seamlessly with old. Odd windows found in the cellars were recycled as overdoors, allowing more light to stream down into dark upstairs corridors. An entirely new staircase was designed by Ptolemy in period style to give easy access to the attics and roof void. In one of the bedrooms, he exposed a Jacobean wooden wall and inserted a little door by the fireplace to allow a glimpse of an older one behind. Paradoxically, it was his mastery of the archaeology that enabled him to integrate the conveniences of contemporary living. These now include a soundproofed cinema hidden down steep stairs behind one cupboard door - 'rather James Bond', says Ptolemy with a laugh - a fully stocked bar behind others and, in the brick-vaulted coal store, a wine cellar.

The true glory of Shanks House lies in its mid-eighteenth-century wing, added presumably when someone in the family enjoyed a large injection of cash. The stucco work around the staircase alone is worthy of Grade-I status, but layers of paint had to be removed to reveal its exceptional quality. Ptolemy ensured its protection by replacing the leaking flat roof over it with a hipped roof echoing the form of that over the east front. Aspirations to grandeur were further suggested by the long sweep of the entrance hall, now used as a formal dining room, its new status enhanced by a magnificent George III mahogany dining table Sophie purchased at Sotheby's Chatsworth Attic Sale in 2010.

The morning room, facing north-east, retained the finest panelling, a richly stuccoed ceiling and the most impressive marble fireplace in the house. A carpet in shades of pale blue and gold sets the colour scheme. 'I sourced the curtain fabrics or carpets for each room and built the colours of the sofas, walls, etc around them, trying to use different textures,' Sophie explains. In the drawing room, another oriental carpet determined the blue and mauve palette. 'I like to mix antique furniture - mostly inherited from my mother - with contemporary works and pieces from Turkey.' The result is an atmosphere of elegant serenity, sophisticated without being too self-conscious.

Her discerning eye for furniture and textiles further complemented Ptolemy's mise-en-scène on the upper floors. His desire to return rooms to their original proportions was only challenged by the planning authorities in the main bedroom, which had acquired a dressing room at one point in the twentieth century. He won on appeal and it went, uncovering in the process the original chimneypiece and a decorative wall painting of a classical urn. The adjacent room, previously split into two basic bathrooms, became a spacious main bathroom, featuring a shower in an alcove decorated with mosaics.

In the boot room, Hunter wellingtons of every size - a present from Roland's father - stand ready for forays into the gardens, which beckon from every window. Replanned by Tom Stuart-Smith, they stretch out to a lake, re-excavated and now hiding a ground-source heat plant. Deservedly, Shanks House won The Georgian Group's 2015 Architectural Award for the finest restoration of a Georgian country house. It proves that, with the support of experienced conservation officers, enlightened interventions can be made to revivify a historic property without disturbing its genius loci.