Longevity, plus.

BY European standards, the British House of Windsor is a young dynasty. The German Hohenzollerns claimed a lineage extending 400 years, from 1415 to 1918. The Russian Romanovs celebrated 300 years of uninterrupted czardom. Both these two antiquities disappeared in the inferno that engulfed imperialist Europe after the end of the First World War.

The British could claim a continuous line of monarchs since the Middle Ages, but for the interregnum from 1649 to 1666 of the regicide Oliver Cromwell and later his son Richard Cromwell.

In 1714, when the British ran out of Stuarts, they imported a family of Hanoverians from Germany. Under Queen Victoria who as a woman could...