He was a respected judge and a Jacobite plotter: discretion, secrecy and devotion to the cause were his watchwords. She was the party animal who liked to drink and gossip. Their marriage was doomed to end in tears — and so it did. Nearly 300 years ago, the wife of a Scottish aristocrat who was considered a threat to the Jacobite cause was kidnapped by her husband and sent into exile on a Hebridean island, where she eventually died a lonely death.

The tempestuous relationship of James Erskine and Rachel Chiesley, Lord and Lady Grange, has been unearthed this week in Prestonpans, East Lothian, where the couple’s “lost” manor house is being excavated by archaeologists. From beneath the grounds of a modern community centre, the pattern of Preston House has emerged. This early 16th century mansion was to become a haunt of Jacobite plotters in the years after 1715 and later a key strategic site during the Battle of Prestonpans (1745), the most significant victory won by Bonnie Prince Charlie’s army.

Dr Tony Pollard, of Glasgow University’s Centre for Battlefield Archaeology, said that the grand building was home to a husband and wife who were the cause célèbre of Edinburgh for almost 20 years.

“Lord Grange was a high-flying figure on the Edinburgh scene. It’s said he would come here with clan chiefs to discuss the Jacobite cause. If you are looking for the roots of the ’45 rebellion, look no further than Preston House,” Dr Pollard said.

“Lady Grange was a socialite, an ‘It’ girl, and they had a stormy relationship. The implication is that she would go partying, have one glass too many to drink, and her tongue would loosen, and he became worried she would betray him. With the connivance of the clan chiefs, he had her kidnapped.”

In her youth Lady Grange was a wild beauty and married her husband only after he got her pregnant. The couple had dubious family connections. Lady Grange’s father was the infamous Chiesley of Dalry, who murdered the president of the Court of Session; Lord Grange, who at the age of 28 became a Lord of Justiciary, was the younger brother of “Bobbing” John, the Earl of Mar, whose military ineptitude ensured the failure of the Jacobite rising of 1715.

The couple had four children but according to Lord Grange’s friends, his wife’s temper and drunkenness made the marriage insufferable for him. Rumours of Lady Grange’s insanity were probably the invention of her enemies. “Her husband’s friends probably did not appreciate uppity women. We might just call her strong-willed. She knew what she liked,” Dr Pollard said.

In 1730, they parted — a move which brought shame upon Lady Grange — but still her husband feared she would betray his plotting. On his orders, on a January night in 1732, a group of Highlanders broke into her lodgings on Niddry’s Wynd, Edinburgh, and attacked her, knocking out some of her teeth. They tied her up and carried her out “as if she was a corpse”, according to one account.

She was smuggled out of the city in a sedan chair, and then taken by coach via Muiravonside and Loch Hourn, near the Kyle of Lochalsh, to Heisker, a tiny island west of Uist.

As soon as his wife was securely out of the way, Lord Grange announced her death, resigned from the bar and became an MP. He kept at least one mistress around his London digs. Preston House was sold but it would feature again in the Jacobite story, at the battlefield of Prestonpans. Scores of redcoats, corralled against its walls, were slaughtered by rampant Highlanders.

All of these events went unnoticed by Lady Grange. When in 1740, rumours of her captivity finally reached Edinburgh, her husband had her spirited away again, first to Assynt and then to Skye. “After her removal to Skye her mind sunk into idiocy,” reads one Victorian account. “The poor wanderer strolled from place to place supported by the hospitality and tenderness which, in the Highlands, have ever been given a sacred claim to the poor.” After 17 years in exile, she died in 1749.

Posterity has been kinder to Lady Grange than her husband. Her fate inspired generations of poets and writers, from Samuel Johnson to Edwin Morgan. Lord Grange’s career ended in political ignominy and failure, though his reputation for brutal misogyny was assured.

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