Christina was one of the feistiest queens that Europe ever produced. Now Veronica Buckley has produced a splendid account of her wild eccentricities, the fruit of 25 years of fascination with a woman who abdicated from the throne of Sweden, but afterwards plotted to mount those first of Naples and then of Poland.

This 17th-century Catholic convert never married. Rumours about her physical oddities and tastes abounded. Hermaphrodite? Lesbian? Even after a quarter of a century of contemplation, the author is not quite sure. What is certain is that Christina shared the same tough, martial spirit of our own Virgin Queen, although not Elizabeth I’s taste in gowns and pearls.

The duc de Guise told a friend that: ‘She wears men’s shoes, and she sounds and moves like a man.’ Christina often behaved like the fiercest of kings, breaking upon the wheel those who displeased her at a time when that punishment was rather going out of fashion further south. Having reigned in Stockholm ? even luring poor Descartes to a would-be fashionable but frozen court, where he died from flu ? she fled to Brussels and into the arms of the Jesuits, en route to the Pope himself.

At that point, this book, the author’s first, overcomes the turgidity of its treatment of the admittedly fiendish complexities of the 30 Years War and finds its stride, exactly as Christina did, taking Rome, then Paris by storm, thereafter criss-crossing Europe. The rest is an extraordinary story, engagingly told.