The 300th anniversary of the union of England and Scotland fell on Tuesday, May 1—in a sense, the birthday of the United Kingdom of Great Britain. The Act of Union of 1707 provided for the amalgamation of the two parliaments at Westminster, the Hanoverian—hence Protestant—succession, and the creation of a single flag, the Union Jack.

It may seem strange to American eyes that the English show no desire to commemorate what is in effect their country’s tricentennial. But there remains deep resentment in some quarters at the overrepresentation of Scots at Westminster and the constitutional anomaly (known as the “West Lothian Question”) that allows Scottish members of Parliament to vote on English legislation but not vice versa. Meanwhile, north of the border, the bitterest opponents of the union—the Scottish Nationalists—are predicted to become the largest party in the newly resurrected Scottish parliament when Scots go to the polls this Thursday.

These matters may seem highly parochial today. And even if Scotland were to vote for independence in a referendum, it would be greeted south of the border with a shrug: English taxpayers are quite aware how generously they subsidize their Scottish counterparts. But there was a time in the 17th century when relations between England and Scotland had implications far beyond either realm.

The original union of 1603, which brought together the two kingdoms under the Stuart dynasty but preserved both as separate and intact realms, had enhanced the power of the monarchy. In 1641, however, a second union, with a very different purpose, was agreed by treaty. This Anglo-Scottish union was the work not of King Charles I but of the two parliaments in Westminster and Edinburgh.

According to The Noble Revolt: The Overthrow of Charles I (Weidenfeld and Nicolson), the magnificent and authoritative new history by John Adamson, the creation of this Anglo-Scottish union was “perhaps the deepest challenge to traditional monarchical authority, at least as it had been exercised in the half century to 1640.” Charles I was deliberately excluded from the treaty negotiations, the prime objective of which was “to ensure that London-based monarch’s permanent constraint.”

At the solemn inauguration of the 1641 union, a sermon was given by Jeremiah Burroughes, a famous Congregationalist preacher and a believer in elective monarchy on the Polish model. The union, he declared, would secure the new constitution created by the Triennial Act, whereby the power of the king to summon parliaments had been abolished in favor of automatic elections every three years.

Under the new union treaty, each parliament could call on the other for military aid against the king, and it was this threat of insurrection that Burroughes had in mind when he proclaimed that “God hath put in a barre to this our doore of hope, to keep it from being shut.” And the effect of the union was, in the view of the Venetian ambassador Giustinian, to promote “Dutch”—that is, republican—“forms of government” among the English, “for which the people here show far too much inclination.”

Already in September 1640, even before the treaty, the English rebels were making plans to raise a joint Anglo-Scottish force, to be known as the “Armies of the Commonwealth”—thereby usurping the prerogatives of the monarchy. Adamson calls this plan “unambiguously treasonous” and argues that the parliamentarians were intent upon reducing Charles I to what he calls a “Duke [Doge] of Venice,” a mere figurehead.

In many respects, the formation of the Anglo-Scottish union in 1641 and the civil war that began in the following year anticipated the events of the American Revolution. (Just as the Constitution of the United States is a working-out of ideas originally generated by the British crisis of the mid-17th century and further enunciated by European thinkers from Hobbes to Locke and Montesqieu.) Americans may be forgiven for being a little hazy about this part of their history, but their ancestors in the 1770’s knew it very well indeed. And Americans, at least, have more excuse for their ignorance than the British, most of whom seemingly neither know nor care about the origins of their own liberties. Nobody buys an antique without informing themselves of its provenance. But we treat our freedom as if its history did not matter.