Herbert was a Guardian of the young King Edward VI after the death of Henry VIII in 1547. As an executor of Henry's will and the recipient of valuable grants of land, Herbert was a prominent and powerful person during Edward's reign, with both the protector Edward Seymour, 1st Duke of Somerset and his rival, John Dudley, angling for his support. He threw in his lot with Dudley, and after Somerset's fall obtained some of his lands in Wiltshire. He was made a Knight of the Garter in 1549, and created Baron Herbert of Cardiff on 10 October 1551, and 1st Earl of Pembroke (of the tenth creation) the following day, by Edward VI.