With its sturdy L-shaped keep and towers, and turrets thrusting from every wall, Strathieburn Castle could be the home of a hero from a Sir Walter Scott novel. Inside there is the same sense of romance and history, with flagstone floors, massive beams and polished wall panels.

Such houses can be hard to date, since they have a multiplicity of layers reaching back into the mists of time. But Ian Guthrie knows exactly when his home was built. “The oldest parts date from 1985,” he says.

It takes conviction to design a modern house in a style four centuries old. While mock-Georgian is commonplace, faux-medieval is considered strange. This is a pity, since castellated architecture is the closest Scotland gets to having a national style. Charles Rennie Mackintosh was well aware of this — and there’s more than a touch of homage to his designs in the entrance to Strathieburn.

The house, which is near Banchory, Aberdeenshire, fools most visitors. “They simply can’t believe it when they hear the truth,” says Guthrie, an oil executive from Aberdeen. He bought the house four years ago from an architect who had built it as his dream home before retiring abroad.

“He spent years hunting down reclaimed materials: carved stone corbels from demolished towers; flagstones from a church; a 16th-century fireplace; oak beams and panelling. The house may be modern, but much of the fabric is genuinely old.”

It was also, when he bought it, lacking many modern comforts. “A real castle is supposed to be cold and austere, and that’s exactly how it was when we arrived,” says Guthrie. “A major renovation was required to install central heating, double-glazing and improved facilities, along with a revamp of the decor.”

Strathieburn is fun. However well it may deceive, it is not a precious relic that imposes rules and standards on anybody who dares to live there.

It is a contemporary, comfortable and practical, yet decidedly unusual, five-bedroom house that plays with historical themes. And if you want to paint the windows pink or alter the front door, you won’t have Historic Scotland descending on you like a ton of hand-made bricks.

A tougher but far more exciting option for the castle lover is to find a ruin and restore it to a habitable state. This is what happened at Eilean Donan a century ago, when Colonel John MacRaeGilstrap transformed the battered castle’s few upstanding walls into what was then a modern home, but is now seen by coachloads of visitors as the epitome of medieval romance.

Queen Victoria had launched the trend in the 1840s, when she and Prince Albert transformed a harmless little mansion at Balmoral into a Scots baronial-style castle. Her subjects, or those who were rich enough to buy into her Highland dream, were quick to follow her example, sometimes with more passion than good taste. Unnecessary battlements were tacked onto roofs, harled walls were stripped to the grim, bare stone and a strange belief took hold that dead stags made attractive interior features.

But sometimes the Victorians showed better form, and castles that would otherwise have been lost were saved. Barcaldine Castle, near Oban, is a good example. A compact, white-harled tower of great dignity set above Loch Creran against a backdrop of mountain peaks, it was built in the late 16th century by Sir Duncan Campbell of Glenorchy.

By the early 19th century, the castle, as with many of its kind, fell victim to the fashion for classical design when the family moved into elegant new quarters at Barcaldine House.

Another twist of fashion saved the crumbling pile, when Sir Duncan bought it in 1896 and spent more than 10 years on its restoration. It is still in the family and, for the past few years, Sir Roderick and Caroline Campbell have been entertaining bed-and-breakfast guests in its handsome rooms.

“It’s terribly sad to be leaving such a wonderful home,” says Lady Campbell, “but now that our daughters have grown up, it’s time to reshuffle.” So, with some regret, the couple will be leaving their comfy country house that has, among its many modern-day amenities, a proper dungeon underneath the hall.

Such restorations are still possible today, but with modern rules and regulations they are much harder to achieve. That is why Castle Tioram, in Moidart, remains a ruin, and one that is now in desperate need of saving, more than a decade after plans were first produced to restore it as a private home.

The first rule for any would-be castle-saviour is: don’t get on the wrong side of Historic Scotland.

The second is: be patient. That at least appears to be the lesson from two ruined castles that are for sale on opposite sides of Scotland.

Drivers on the M9 out of Edinburgh have for many years sped past a ruin cloaked in scaffolding close to the turning to the Forth Road Bridge.

This is Duntarvie Castle. Dating from the 16th century, it was home to Alexander Durham, an ambitious civil servant in the Stuart court who reached the peak of his career in 1567 when he was appointed master of the prince’s wardrobe by Mary, Queen of Scots.

In a neat example of historical symmetry, its remains now belong to Geoffrey Nicholsby, an Edinburgh kilt-maker who has spent the past 20 years fighting for consent to restore them as a baronial headquarters for his business.

“I thought Historic Scotland would be delighted with my plans,” he says. “In fact it’s been a battle all the way, a long and costly struggle. One inspector even told me that he would rather I kept it as a ruin.”

Now, at last, the plans have been approved, but for Nicholsby the victory has come too late. “I’m 62. I don’t want a castle any more. I want a yacht in the Caribbean.” So it’s up to somebody else to realise the project and bring Duntarvie back to life.

Over in the west, near Turnberry, in Ayrshire, Baltersan Castle was built in 1584 by John Kennedy, a member of the same, notoriously ruthless family that later employed Robert Adam to build Culzean.

Indeed, Adam sketched the ruins of Baltersan when seeking inspiration for his own designs and so, too, in the 1890s, did Mackintosh. For the past 15 years it has been owned by James Brown, a local businessman who has dreamt of living in a castle since he was a boy.

“I’ve been through two appeals, I’ve shifted 1,000 tonnes of rubble and I’ve spent about £150,000,” he says. He has also been on Dragons’ Den in a bid to raise the funds required to restore the still-roofless shell as an exclusive private club, providing accommodation for the region’s wealthy golfers.

“Duncan Bannatyne was tempted, but he wanted almost all the equity.” Now everything’s in place: plans, approvals, even the offer of a £500,000 restoration grant from Historic Scotland. But, as with Nicholsby, he’s lost the will to take the project on to the next stage.

“It needs an eccentric millionaire,” he says, “and unfortunately I fulfil only half of that equation.”

More than any other kind of architecture, castles exert a magical allure. They link us to our history and our childhood dreams, they symbolise defiant dignity and pride. It is estimated that Scotland has at least 3,000, ranging from little more than piles of stone to masterpieces such as Craigievar. And those are only the ones that are genuinely old. Strathieburn is not the only modern castle deceiving all but the most knowledgeable eyes.

Ian Begg, an architect, has devoted much of his professional career to restoring Scottish castles. Now he has retired to a tower house in Plockton that he built from scratch.

“I’ve reached the age when I need a lift rather than a turnpike stair,” he says. It seems that there is no limit to what can be achieved using Scotland’s own distinctive architectural style.

Strathieburn Castle is for sale through Knight Frank, 0131 222 9600, at offers over £1m;

Barcaldine Castle, offers in the region of £1.35m, Savills, 0131 247 3711;

Baltersan Castle, offers over £195,000 Strutt and Parker, 0141 225 3880;

Duntarvie Castle, no guide price, Strutt & Parker, 0131 226 2500

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