Charles II, with his roving eye, set the ball rolling. He recompensed his mistresses from moneys earmarked for his secret service, and as a result ended up footing the bill to supply his own secrets to his enemies. When the nubile young Frenchwoman Louise de Keroualle appeared at his court (in all probability sent by Louis XIV to spy) Charles wanted her for his mistress. She coyly resisted, but eventually surrendered and was soon passing on the secrets she learnt on the King's pillow.
Her treachery cost both Charles and Louis dear, earning her no less than pounds 600,000 from the two kings in a single year, it was said. And Charles created her Duchess of Portsmouth while Louis made her Duchesse d'Aubigny.
Small wonder the secret service was without funds when the London government needed an intelligence network to counter the Jacobites after the Glorious Revolution. It took years to build up an effective "MI6" operation to fight the Jacobite threat, and skilful use of intelligence was a key factor in the Stuarts' defeat.
Spying in the 18th century was motivated by money rather than political conviction. Under Sir Robert Walpole during the 1720s the post was able to intercept practically every letter arriving from Europe. His "secret man" who ran this operation was so skilled that his staff could open a letter, read it, reseal it, and pass it on without the recipient realising it had been tampered with.
Over the Jacobite century the Hanoverian government gathered together a colourful portfolio of spies and double agents. They may not have had an 007, but Agent 101, a Frenchman named Francois de Bussy, blew apart France's planned invasion in 1744 when he handed over every detail of the operation, and it was called off. Its failure led to the angry young Bonnie Prince Charlie's sailing for Scotland - and the disaster of the '45 rising - the following year.
Dudley Bradstreet was many things before he turned to intelligence work - adventurer, pimp and card-sharper. His big chance came when Prince Charlie marched into England. Bradstreet was sent north, dressed as a gentleman, to insinuate himself into the Jacobites' war council at Derby, and there he sowed the seeds of a non-existent army marching towards them, which proved a key factor in persuading the rebels to return to Scotland.
Money drove young Alasdair Macdonnell of Glengarry to act as a double agent and betray the last serious attempt to overthrow King George II. Glengarry, who signed himself "Pickle the Spy", caused much more harm to Prince Charlie's cause than wrecking the Elibank Plot to capture the Hanoverian royal family: he lost the Prince much of his following by casting the blame on someone else.
Charles had just brought Clementine Walkinshaw to live with him as his mistress, and, by sheer bad luck, she had a sister who was on the staff of the dowager Princess of Wales in London. As a result every Jacobite was convinced that Clementine was the "mole" who leaked the Elibank secrets to London. They demanded that Charles should get rid of her, but he refused, and followers began to desert the cause in droves.
It took a century and a half's detective work to trap Pickle. The 19th- century writer Andrew Lang compared Pickle's letters with those of young Glengarry and discovered one startling similarity - both always wrote "how" for the word "who". The final betrayal of the Stuart cause had not come about through a mistress's pillow talk: they had finally been shafted by one of their own needy Highland chiefs.
Hugh Douglas is the author of `Jacobite Spy Wars: moles, rogues and treachery' (Sutton Publishing, pounds 19.99)Reuse content