Indeed it took a good deal less than a century: only a decade after the 1812 war London was proposing a joint declaration against Europe's monarchies seizing territory in the Americas; Monroe chose to go it alone, but Britain backed the policy despite implicitly being among those being warned off. Trade shows a still faster recovery in the 1780s and 1810s: within a few years of each war you'd think nothing had happened.

Besides the obvious affinities between their ruling elites, part of the explanation is that with the US renouncing any involvement in Europe's affairs and preoccupied with westward expansion across the North American continent, there was for a century little basis for friction once British rue was gone, apart from the 1840s border dispute, Civil War complications and the brief Venezuela flurry. The two powers shared a distaste for European rivals' imperial designs, Washington wanting to keep Europe "over there" while London prized commercial access to non-European lands, a growing US priority too by mid-century: nor until the 1940s did the US show any inclination to assume the global financial leadership claimed by Britain.

It was ultimately a marriage of convenience, based in the first century on broadly compatible strategic and commercial perspectives, and in the second on waning British capacity to go it alone as others challenged its industrial lead and - unthinkably - its naval supremacy. Once Britain abandoned any fantasies of reconquering its lost North American colonies and US hotheads were talked out seizing Canada, there was little to do but make the best of it.