In this world nothing can be said to be certain,” observed Benjamin Franklin, “except death and taxes.” And in the 1950s, for some of Britain’s hitherto wealthiest families, the two came together with devastating effect. Already under pressure from falling income, rising general taxation and the horrendous running costs of their family homes, death duties were often the final straw. The country pile had to go.

Some of these large and often beautiful country houses were sold but before the Big Bang and current huge sums to be made in the City, the market for houses that might cost £100,000 a year in upkeep was soft to say the least. Many simply fell into disrepair and were ultimately demolished, depriving the nation of some of its loveliest country architecture.

However, in the country house’s darkest hour came a saviour for some at least – the Country Houses Association which was set up in 1955 to provide shared accommodation, with communal meals, for well-to-do retirees in good health in a style to which many residents had formerly been accustomed. The first house to be bought and converted, in 1956, was Danny House near Hurstpierpoint in Sussex. Next, in 1959, was the grade-I listed Aynhoe Park in Northamptonshire. These set the pattern which was successfully repeated with other houses, some of which still exist as retirement communities today.

Despite the ultimate collapse of the CHA scheme, it had proved that yes, for the country set, there was life after death duties. The idea of multiple occupancy was taken up and adapted by the Period and Country Houses, a company that focused on creating independent units within the house and estate buildings. The idea caught on and developers began converting country houses throughout England into apartments.

Alas, many of these conversions were not hugely successful, indeed some were complete pig’s ears. The major problems were that either the developer simply tried to cram too many apartments into the building or thought laterally rather than vertically, converting on a floor-by-floor basis so that only a few apartments benefitted from the elegant ground floor reception rooms. The real turning point came in the late 1970s when architect Kit Martin began converting vertically providing occupants with a considerably more varied layout.

All of which has been great news for Dan and partner Chris, both doctors – Dan of Sociology and Chris, Medicine. Three and a half years ago they decided to sell a home in Camberwell, let out a second home in Canterbury and buy together. At first, Surrey wasn’t even on their radar but wandering through properties online, a property caught their eye – an elegant apartment on two levels called East House, in a Victorian country house known as Mynthurst Mansion near Leigh, originally the great house of one of the largest estates in Surrey. They decided to have a look. “It was a lot further out than we’d originally planned but we saw it and just fell for it,” says Dan. “It was a beautiful apartment and had so much potential.”

This potential lay not in the options for knocking down walls and remodelling rooms but in the sheer variety and flexibility of both the rooms as they stood and the layout of the flat as a whole. The couple went back to scratch, approaching the apartment as merely a range of spaces, and decided what would suit them and their lifestyle best. Rooms would have to change their function – the master bedroom, for instance, would become their drawing room – and there would be selective redecoration from top to bottom.

The result is truly inspiring – a place of beauty, originality and fascination from the vast stained glass window which graces the old main staircase which leads up to the apartment door to the guest room at the top of the house that the couple now offer on airbnb. It is a home where style triumphs effortlessly over fashion. “I like things I’ve never seen before – in other people’s homes or wherever – things perhaps other people don’t want so they will be unique and, of course, cheap,” says Dan.

The original Victorian master bedroom suite now has oak kitchen units and blue granite work surfaces and a floor of white-painted boards. The simple pine table – originally Irish but brought over by Dan from his native Australia – has been elegantly upgraded by giving it a glass top and surrounding it with chic white Ikea chairs. Beside the fireplace lazes a warm wood and white armchair which Dan restored himself and above it a collection of favourite gilt mirrors and antique coffee grinders.

In the hallway is perhaps Dan’s pièce de résistance, a superb Gothic stained glass window through which one has a superb view of the monumental window on the main staircase below. “It used just to be a modern square window and I thought it deserved something more sympathetic,” says Dan, noting that he copied the leaf motif from an original above the front door.

Off the hallway is a seriously cool urban shower room the couple created by knocking the old shower and WC into one. The floor and walls are black slate, cleverly sourced by Dan for 5p a tile, and in the shower itself a panel of Venetian glass tiles which Dan admits were, alas, far from cheap.

Nearby is the TV room which has a light mid-century touch in terms both of colour palette and the considerable presence of a superb white Barcelona chair and foot rest. A comfortable purple sofa and red rug, curtains and a wonderful side lamp Chris has made from an antique fire extinguisher complete the period picture.

What was the apartment’s original study/library is now the couple’s elegant but intimate dining room. “We had to do quite a bit of work here,” says Dan. “To begin with the original fireplace had been removed so we put in a black marble fireplace and replaced the flooring with reclaimed herringbone parquet.”

The latter were originally too thick and would have raised the floor level above that of the hallway so each block had to be trimmed exactly to the right height. The 1840s Victorian circular table is attended by Regency chairs Dan had reupholstered in black damask. On the wall is a set of reindeer antlers and above the chimneypiece a case of butterflies and a stuffed owl. “Chris calls this my dead and dusty room,” observes Dan.

And so on up a lovely original staircase hung with a bespoke string of paper lanterns to the top floor, part of which was probably the original family’s children’s bedrooms and perhaps the nursery. These three rooms now form the couple’s B&B suite – bedroom, bathroom and a large drawing room. “B&B has been a great success for us and we enjoy meeting new people but we’ve decided to limit visits to a couple of times a month. As an intensive care consultant Chris has a demanding job and works long hours so it’s important that his time at home is as relaxing as possible.”

The beamed bedroom had been at some point remodelled in Arts and Crafts style and Dan has run with this adding a further dimension with touches that again underline his creativity and talent as a designer. The hand basin is a particular triumph, the basin itself a beautiful Victorian jam pan, its base an old science lab table and the finished article, utterly stunning. “It seemed sacrilege to cut a hole in that wonderful pan,” he said, “but it gave it a whole new purpose and lease of life and I think it works.” Works? I should coco.

Next door is a predictably lovely bathroom in Victorian style complete with roll-top bath, twin basins and high cistern loo. Dan declares the drawing room – once used as a dance studio – a “work-in-progress” but a mere mortal would see it as a highly stylish job done. Two huge grey velvet Habitat sofas recline on black cow hides facing each other across a long glass table. In the window hang matching grey velvet curtains and the whole scheme is perfectly set off by the original deep red tiled fireplace.

Also on this floor is a guest room which is occasionally offered to B&B guests requiring space for friends or children and decorated in French Empire style à Dan. Above the bed is a panel of pretty pale blue wallpaper and a patinated antique French mirror and, standing by, is a pair of mother-of-pearl inlaid chairs reupholstered in blue. Dan has painted the floor in black gloss.

The final room is the couple’s own bedroom – all greys, pale blues and turquoise warmed by glowing polished oak floorboards, a proud Paul James cow surveying all from above the chimneypiece. The positioning of the bed by the beautiful Gothic mullion window gives it a stunning headboard of sky or stars depending on what hours you keep. And an interesting historical footnote is hiding under the rug – a trap door that houses the winding mechanism that allows the vast chandelier over the house’s main staircase to be raised and lowered for cleaning.

This is a house in which no two rooms are remotely the same. Styles range from contemporary cool through Victorian, Arts and Crafts and Empire and yet Dan has handled each with deft confidence, never merely producing period pastiches but interpreting each, surprising and delighting with his talent and originality.

It is perhaps sad that over the years so many period country houses have had to be converted to save them from the wrecker’s ball but when one sees what Dan and Chris have done here it is utterly impossible not to celebrate the reincarnation of East House and the unique new home it has given them the opportunity to create.