John of Gaunt III's rule was becoming unpopular due to high taxation and his affair with Alice Perrers, political opinion closely associated the Duke of Lancaster with the failing government of the 1370s. Furthermore, while King Edward and the Prince of Wales were popular heroes due to their successes on the battlefield, John of Gaunt had not won equivalent military renown that could have bolstered his reputation. Although he fought in the Battle of Nájera (1367), for example, his later military projects proved unsuccessful. When Edward III died in 1377 and John's ten-year-old nephew succeeded as Richard II of England, John's influence strengthened.
Succession to Elizabeth I of England John of Gaunt, would claim the throne and so overturn the principle of primogeniture, was revived in the context of the Elizabethan succession, after seven generations. John of Gaunt's eldest daughter having married into the Portuguese House of Aviz, one of his descendants was the Infanta of Spain, Isabella Clara Eugenia. The legitimacy of Isabella's claim was seriously put forward, on the Catholic side of the argument. A reason given for Essex's Rebellion was that the Infanta's claim had gained traction with Elizabeth and her counsellors. The Succession to the Crown Act 1543 was the third such act of the