Rich became close to Charles, installed as heir to the throne when Prince Henry died in 1612, as well as his favourite, the Duke of Buckingham. He took part in various diplomatic missions and briefly served as a volunteer in the Eighty Years War, before being created Baron Kensington in 1623. The next year he was made a member of the Privy Council of England, and sent to Paris to help negotiate the marriage contract between Charles and Henrietta Maria of France, a process completed by James Hay. When Charles succeeded his father in March 1625, Hay was made Earl of Carlisle and Rich Earl of Holland, taking his title from an area in Lincolnshire.