She-Wolves, By Helen Castor

A masterful account of Elizabeth I's predecessors

Henry VIII's obsession with producing a male heir produced one of the most crucial, best known chapters in English history. In pursuit of a boy he divorced one wife, killed another and broke from Rome. She-Wolves: The Women Who Ruled Before Elizabeth opens dramatically in 1553, on the deathbed of that male, Edward VI. After which, every branch of the family tree ended in a woman; each of nine potential claimants embodying the paradox that is the central question of Dr Castor's vivid and impressive book. How could a woman be a king? How could something so "repugnant to nature", in John Knox's words, be tolerated? Castor illuminates the resolution of the Tudor succession crisis by considering the careers of four women who, between the 12th and the 15th centuries, wielded royal power with varying degrees of talent and success.

Henry I's declared successor, his daughter Matilda, made it as far as Westminster, but her hopes of becoming a monarch were destroyed when she made the mistake of acting like one. As "Lady of England", domina, Matilda was required to exercise dominium, but the behaviour expected of male rulers was read by contemporaries as monstrous arrogance, and Matilda found herself outfoxed by the wife of her rival, Mathilde of Boulogne, who carefully spun her own political manoeuvrings as meek expressions of feminine supplication.

Matilda's daughter-in-law, Eleanor of Aquitaine, managed to remain at the centre of European politics between the ages of 13 and 78, negotiating the pitfalls of female power with brilliant success. Castor's meticulous comparisons of chronicle accounts dispel much of the rumour which swirls around this notorious figure, and by concentrating on statecraft rather than scandal, she produces perhaps the most accurate and compelling portrait of Eleanor in popular history to date.

Castor's handling of Isabella of France, whose husband, Edward II, neglected her in favour of his lover, Piers Gaveston, is equally dextrous. Isabella's achievement of the hitherto unthinkable, the deposition of an anointed monarch, is often overlooked in favour of juicy historical gossip involving red-hot pokers, but Castor presents an insightful portrait of a woman who expertly manipulated the legitimacy of royalty to deliver England from tyranny. Despite her ruthless reputation, Isabella ended her days honoured and wealthy, unlike Margaret of Anjou, who battled to secure her son's crown in the face of the inertia of her saintly dud of a husband, Henry VI.

She-Wolves draws on the precedents established by all four women to confront the conundrum with which England was presented in 1553. Castor's emphasis on political strategy is refreshing in a field where women's decisions are often read as emotionally generated, and her translation of thorough primary-source research into gripping narrative is impressive. This is a brilliant story supported by brilliant scholarship, particularly in its conclusion, where Castor delineates the way in which Mary Tudor, England's first queen regnant, manipulated perceptions of female power to bring herself safely to the throne.

The first bonfires lit in London for Mary were for celebration, not heretics, and though Mary's reign descended into infamous intolerance, Castor's portrait is sympathetic to the exigencies of her unique position. In terms of sovereignty, her marriage to Philip of Spain is revealed as prescient, rather than misguided, since a ruler could not submit as a wife to a subject. Nevertheless, it was that marriage which destroyed Mary's popularity. Mary's sister committed no such error.

In considering 400 years of female royal power, Castor draws together not only four innovative biographies, but the strands of law and precedent so expertly woven into legend by Gloriana, the greatest of Knox's "monstrous regiment of women".

'Queens Consort: England's Medieval Queens' by Lisa Hilton is published by Phoenix