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.

A fundamental reason why Britain was not torn apart by civil war after 1688 was that its inhabitants' aggression was channelled so regularly and so remorsely into war and imperial expansion abroad.

Most Britons still lived and died without encountering anyone whose skin colour was different from their own. Slaves, in short, did not threaten, at least as far as the British at home were concerned. Bestowing freedom upon them seemed therefore purely an act of humanity and will, an achievement that would be to Great Britain's economic detriment, perhaps, but would have few other domestic consequences.

Virtually every war fought since the Act of Union had gone badly at some stage, but before 1783 none had ended in defeat. Nor would any major war in which Britain was involved after this date end in defeat. Those who are curious about this country's peculiar social and political stability probably need look no further than this for essential cause.

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.

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.

Contrary to received wisdom, the British are not an insular people in the conventional sense - far from it. For most of their early modern and modern history, they have had more contact with more parts of the world than almost any other nation - it is just that this contact has regularly taken the form of aggressive military and commercial enterprise.