When Edmund's son Thomas, 2nd Earl of Lancaster, inherited the estates and title of his father-in-law Henry de Lacy, 3rd Earl of Lincoln, he became at a stroke the most powerful nobleman in England, with lands throughout the kingdom and the ability to raise vast private armies to wield power at national and local levels. This brought himand his younger brother Henry, 3rd Earl of Lancasterinto conflict with their first cousin King Edward II, leading to Thomas's execution. Henry inherited Thomas's titles and he and his son Henry of Grosmont, 1st Duke of Lancaster, gave loyal service to Edward's son King Edward III.