She was twenty when her husband died and her baby became King of England. Her marriage had been written into a treaty over two kingdoms. Even in widowhood, her next marriage was thought too important to leave to her.

Catherine of Valois was born in Paris on 27 October 1401, at the Hôtel Saint-Pol, a daughter of Charles VI of France and Isabeau of Bavaria. Her father had suffered recurring attacks of mental illness since 1392. There were intervals in which he could govern, and others in which royal government had to continue without him. She was born into a royal house where the king's health was a matter of state.

As she grew up, the struggle between the royal houses of Burgundy and Orléans deepened into civil war. Across the Channel, the English crown maintained its own claim to France. A marriage between the kingdoms offered one way of arranging a peace, and a French king's daughter was among the things that could be brought to the negotiating table.

In May 1420, the Treaty of Troyes set out what that peace was to look like. Henry V of England would marry Catherine. Charles VI would keep his crown for the rest of his life, but Henry would govern France and succeed him. After that, the two kingdoms would have one sovereign, while keeping their separate laws and customs. The arrangements reached beyond the bride and groom to their children and the children who would follow them.

There was already a French heir. Catherine's brother Charles, the dauphin, was to be excluded. The treaty made room for her husband by shutting out her brother, and it could arrange the succession on parchment without making everyone accept it.

Catherine married Henry at Troyes on 2 June 1420. She was eighteen. The treaty spoke of their marriage as a bond made for peace and turned her parents into Henry's father and mother. The language was familial, almost domestic, for an agreement disposing of a kingdom.

The following February she was crowned at Westminster Abbey. By the summer Henry was back in France with his war, and in December she gave birth at Windsor to their son, also called Henry. His father never saw him. The marriage now had the child through whom its promises were meant to continue. In May 1422 Catherine crossed to France to join her husband, leaving the baby in England.

Henry V died at Vincennes on 31 August 1422. Their son was eight months old. Within weeks, Charles VI was dead as well, and the baby was claimed as King of France under the settlement made before his parents' wedding. His mother was the daughter of one dead king and the widow of another. Her brother claimed the French throne against her child.

She had been married for little more than two years.

Catherine accompanied her husband's body back to England. At his funeral in Westminster Abbey, four horses drew the chariot carrying his coffin into the nave as far as the choir screen. The marriage that had promised a shared future for two kingdoms had brought her back across the Channel in a funeral procession. The husband was gone.

In England, government proceeded in her infant son's name. A new husband for his mother could acquire a position uncomfortably close to the throne. For the lords managing the minority, her remarriage threatened to alter the balance between them. Widowhood had ended her marriage. It had done nothing to end their interest in it.

In the Parliament of 1427-28, a measure was put forward requiring the king's permission before a man married an English queen, with the king himself old enough to exercise discretion. A husband who proceeded without it was to lose his lands and goods for life. Catherine's son was still a small boy. The proposed arrangements left her future waiting upon his capacity to approve it.

She married again.

Her second husband was Owen Tudor, a Welsh squire. This was a very different match from the one celebrated at Troyes. There was no kingdom attached to Owen's hand, no equivalent rank to set beside hers. Around 1430 the widowed queen married him in secret, and no record of the wedding has survived. Their sons included Edmund and Jasper, younger half-brothers of the King of England.

Catherine died at Bermondsey Abbey on 3 January 1437. She was thirty-five. Edmund and Jasper were still children. She did not live to see her first son make his half-brothers earls, Edmund of Richmond and Jasper of Pembroke, or Edmund marry Margaret Beaufort, or to know the grandson born to them in 1457, another boy named Henry.

That grandson's claim to the English throne came through his mother, Margaret. His connection to Catherine belonged to the other side of his family: Edmund was the son of the French queen and her Welsh husband. In 1485 he defeated Richard III at Bosworth and became Henry VII, the first Tudor king.

Catherine had been twenty when her baby became king, and thirty-five when she left Edmund and Jasper behind. The grandson born twenty years after her death belonged to the family she had begun with a Welsh squire. He took the same crown her first child had inherited in his cradle.