Hilton leads the reader through a colourful pageant of English Queens from Matilda of Flanders to Elizabeth of York spanning the time from William the Conqueror to Henry VII. As Queens Consort, these women had no predefined role or any constitutional power, but like the First Ladies in the United States today, they defined their roles according to their interests.
For a king, the choosing of a wife was a highly political affair. Henry III thought that the main point of royal marriage lay in the strengthening of political ties. For Edward III childbearing was the main point when he chose to marry Philippa of Hainault because of her broad hips, rather than her sister. He was proven right in the event, as the marriage showed nine surviving children to its credit. John of Gaunt, one of their sons, is ancestor to a huge proportion of people in England, as well as to the Queen and the aristocracy.
But Hilton is more interested in the women's side of the bargain. Her investigation brings forth the history of these remarkable women quite at odds with their demure portraits, their aloof tombs, or the saint-like images in ancient texts. Living in the heart of power they had power. Each of them used it in her own fashion.
Hilton highlights the ambiguity of the role as Queen Consort and provides a full portrait of each of the Queens. She forcefully dispels any idea one might have had about powerless medieval brides used as pawns in diplomacy. These women had clout and used it, as shown by Eleanor of Aquitaine who was probably the most powerful woman of her time.
For Hilton, the main outflow of this queenly power manifested itself in pleading for mercy, in interceding, and in charity, thereby providing a counter-balance to the absolute power of the king. The most famous incident of all is Philippa's rescue of the citizens of Calais in 1347. The incident has been commemorated as late as 1889 by Auguste Rodin in a monumental bronze ensemble, or 1914 in a play by Georg Kaiser.

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It is a mixed lot that is presented in the book, obviously. It took me longer than normal to read it, because keeping all the Isabellas and Matildas straight is an effort. Hilton helps hugely with this by providing detailed genealogies to sort them into the time frame. All the same I was swearing more than once at unimaginative medieval parents.
The book is a good read and makes one want to know more about these women at the centre of power.