Loyal and substansial Catholic service on the battlefield undermined one of the most longstanding objections to emancipation: namely, that since Catholics owed religious allegiance to a foreign authority in the person of the Pope, their political and patriotic allegiance must necessarily be suspect.

Jacobitism involved much more than a debate about the merits of a particular dynasty. Men and women were well aware that its success was almost certain to involved them in civil war. And the more politically educated knew that the Stuart Pretender was a pawn in a worldwide struggle for commercial and imperial primacy between Britain and France.

These developments - a massive transfer of land by way of inheritance and purchase, an unprecedented rise in the profitability of land and increasing intermarriage between Celtic and English dynasties - helped to consolidate a new unitary ruling class in place of the more separate and specific landed establishments that had characterised England, Scotland, Wales and Ireland in the Tudor and Stuart eras.

From the 15th century to 1688, England and Wales, like Scotland, had been peripheral kingdoms in the European power game, more often at war with each other that with Continental powers, and - except under Oliver Cromwell - scarcely very successful on those occasions when they did engage the Dutch, or the French, or the Spanish.

Recognising that an ostentatious cult of heroism and state service served an important propaganda function for the British elite does not mean, of course, that we should dismiss it as artificial or insincere. All aristocracies have a strong military tradition, and for many British patricians the protracted warfare of the period was a godsend. It gave them a job, and, more important, a purpose, an opportunity to carry out what they had been trained to do since childhood: ride horses, fire guns, exercise their undoubted physical courage and tell other people what to do.

It would be wrong to interpret the growth of British national consciousness in this period in terms of a new cultural and political uniformity being resolutely imposed on the peripheries of the island by its centre. For many poorer and less literate Britons, Scotland, Wales and England remained more potent rallying calls than Great Britain, except in times of danger from abroad. And even among the politically educated, it was common to think in terms of dual nationalities, not a single national identity.

At one level Great Britain at the beginning of the 18th century was like the Christian doctrine of the Trinity, both three and one, and altogether something of a mystery.