In 1620 he was made Dean of Westminster and was swiftly elevated by King James I to the Bishopric of Lincoln in 1621, as well as being made Lord Keeper of the Great Seal. Throughout his political career Williams was identified as a strong supporter of King James, who, it has been said, valued him as a man "who knew his mind and would do his bidding" and with whom personally he had much in common. He alienated the Prince of Wales, the future Charles I by disapproving of his ill-fated expedition with the Duke of Buckingham to Madrid. When James I died and was succeeded by Charles I in 1625, Williams was quickly removed from the office of Lord Chancellor, and was prevented from attending Parliament. Though Williams managed to survive Buckingham, who was assassinated in 1628, he remained out of favour; he incurred the enmity of William Laud, Archbishop of Canterbury from 1633 and his powerful ally Thomas Wentworth, 1st Earl of Strafford, both of whom had great influence with Charles I.