the earldoms of March and Ulster on the death of his maternal uncle Edmund Mortimer, Earl of March, who had died campaigning with Henry V in France, and the earldom of Cambridge which had belonged to his father. Being descended from Edward III in both the maternal and the paternal line gave Richard a significant claim to the throne if the Lancastrian line should fail, and by cognatic primogeniture arguably a superior claim. He emphasised the point by being the first to assume the Plantagenet surname in 1448. Having inherited the March and Ulster titles, he became the wealthiest and most powerful noble in England, second only to the king himself. Richard married Cecily Neville, a granddaughter of John of Gaunt, and had thirteen or possibly fifteen children: Anne of York (1439–1476)(Mitochondrial DNA taken from a descendant of her second daughter, Anne St Leger, Baroness de Ros, was used in the identification of the remains of Richard III, which were found in 2012.) Henry (b. 1441; died as a child) Edward (1442–1483) Edmund (1443–1460) Elizabeth (1444–1503)married John de la Pole, 2nd Duke of Suffolk; she was the mother of several claimants to the throne. Margaret (1446–1503)married Charles the Bold, Duke of Burgundy. William (b. 1447; died as a child) John (b. 1448; died as a child) George (1449–1478) Thomas (b. 1450/51; died as a child) Richard (1452–1485) Ursula (b. 1455; died as a child) In her will, Cecily stated that Katherine and Humphrey were her children, but they may have been her grandchildren through de la Pole. Conflict over the crown When Henry VI had a mental breakdown, Richard was named regent, but the birth of a male heir resolved the question of succession. When Henry's sanity returned, the court party reasserted its authority, but Richard of York and the Nevilles defeated them at a skirmish called the First Battle of St Albans. The ruling class was deeply shocked and reconciliation was attempted. York and the Nevilles fled abroad, but the Nevilles returned to win the Battle of Northampton, where they captured Henry. When Richard of York joined them he surprised Parliament by claiming the throne and forcing through the Act of Accord, which stated that Henry would remain as king for his lifetime, but would be succeeded by York. Margaret found this disregard for her son's claims unacceptable, and so the conflict continued. York was killed at the Battle