Richard II in the 1390s, which barred accession to the throne to any heirs of the legitimised offspring of Henry's great-great-grandparents, John of Gaunt and Katherine Swynford. Whether such an unprecedented Act had force of law is disputed.. Furthermore, there were legitimate Lancastrian lines into the Royal Houses of Portugal and Castile. Whatever the merits of Henry's claim, according to Vergil, his mother and Elizabeth Woodville agreed he should move to claim the throne and, once he had taken it, marry Elizabeth of York to boost his feeble claim. In December 1483, in the cathedral of Rennes, Henry Tudor swore an oath promising to marry her and began planning an invasion. In 1484, Elizabeth of York and her sisters left Westminster Abbey and returned to court when Elizabeth Woodville was apparently reconciled with Richard III. This may or may not suggest that Elizabeth Woodville believed Richard III to be innocent of any possible role in the murder of her two sons. It was rumoured that Richard III intended to marry Elizabeth of York because his wife, Anne Neville, was dying and they had no surviving children. The Crowland Chronicle claimed that Richard III was forced to deny this unsavoury rumour. Soon after Anne Neville's death, Richard III sent Elizabeth away from court to the castle of Sheriff Hutton and opened negotiations with King John II of Portugal to marry his sister, Joan, Princess of Portugal, and to have Elizabeth marry their cousin, the future King Manuel I of Portugal. Henry Tudor and his army landed in Wales on 7 August 1485 and marched inland. On 22 August, Henry Tudor and Richard III fought the Battle of Bosworth Field. Richard III had the larger army, but was betrayed by one of his most powerful retainers, William Stanley, and died in battle. Henry Tudor took the crown by right of conquest as Henry VII. Queen of England Marriage to Henry VII Though initially slow to keep his promise, Henry VII acknowledged the necessity of marrying Elizabeth of York to ensure the stability of his rule and weaken the claims of other surviving members of the House of York. It seems Henry wished to be seen as ruling in his own right, having claimed the throne by right of conquest and not by his marriage to the de facto heiress of the House of York. He had no intention of sharing power. Henry