It can sometimes seem — unfairly but irresistibly — as if the sole function of the myriad Lilliputian German statelets of the Holy Roman Empire was to provide the royal families of Europe with some of their most dismal consorts. In the century and a half after George I came to the throne in 1714 Britain imported more than its fair share, but if in Caroline of Brunswick we drew quite possibly the rummest of the whole lot, in another and largely forgotten Caroline, Wilhelmine Karoline of Ansbach, the wife of George II, 18th-century Britain and Matthew Dennison struck, if...