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.
The Twelve of England sealed by the marriage of John I of Portugal and Philippa of Lancaster, daughter of John of Gaunt) and before the death of John the Gaunt in 1399. Narrowing the window further, it was probably sometime after 1389, when John of Gaunt returned to England from his failed Iberian campaign, and before the death of John of Gaunt's wife, the Duchess of Lancaster, Constance of Castile in 1394. The common date frequently cited is 1390. The Duchess's Castilian nationality may lend credence to such an event, and her twelve ladies-in-waiting were also, likely, Castilian rather than English, which may explain