An examination of the 1841 census has revealed that the direct ancestors of David Cameron and Gordon Brown both scraped livings from the Scottish soil on farms a mere 150 miles from one another. Yet, while the Browns stayed put in their native Fife, the Camerons from Inverness reaped the financial dividends by following Dr Johnson’s insolent advice that the “noblest prospect which a Scotchman ever sees, is the high road that leads him to England”. Albeit, in Ewen Cameron’s case, by way of Shanghai.

While remote Scots farmers may have struggled to harvest high-yield crops, they have certainly produced their fair share of southern-English-sounding Tory leaders. Harold Macmillan appeared to be the embodiment of a Tory grandee. Like David Cameron, he had been educated at Eton and Oxford. With his lofty manner, he cut an imposing figure in his three-piece tweed suit, pottering around his Sussex mansion, Birch Grove. His father-in-law was the Duke of Devonshire. But like Mr Cameron, his surname was the giveaway to his roots.

Macmillan’s great-grandfather was a Scottish subsistence farmer living in a thatched and extremely poky one-storey croft on the Isle of Arran. Into this inauspicious world of oats and turnip, Duncan Macmillan endeavoured to bring up 12 children in the first years of the 19th century. What little he saved he spent on their education and those not claimed by tuberculosis made the long daily walk to a remote school.

There, wee Daniel Macmillan’s precocity was nurtured. In 1824, aged 11 (his father had died the previous year), he left the island and got a job working in a bookshop on the mainland. After years of grind, he and his brother, Alexander, moved to England and managed to borrow £750 with which they opened a bookshop in Cambridge. It prospered and in 1843 they established the great publishing house, Macmillan. Although Daniel died from consumption in 1857, aged only 44, he had laid the golden egg that ensured his grandson, Harold, would be born into southern privilege.

There was also Scots farming blood flowing in that most English-seeming of interwar Tory prime ministers, Stanley Baldwin. His mother was Louisa Macdonald. Her forebears — via Methodist missions to Ulster and Manchester — had originally roamed the Highland gloaming. They made the most of their limited opportunities. “My great-grandfather on my mother’s side,” Baldwin boasted, “taught himself six languages and educated his elder son to take a scholarship at the University of Cambridge.” It paid off. The great-grandson ended up not only Prime Minister but also Chancellor of Cambridge.

Scots driven by a thirst for godliness, self-improvement and Mammon . . . truly, one of England’s most potent forces.

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