Walpole gladly welcomed the young Newcastle into his coterie because Walpole believed that he could easily control Newcastle and because it would strengthen Walpole's hand against the rival Whig factions. Newcastle joined with Walpole because Newcastle, correctly, believed that Walpole was going to dominate British politics for a generation. In 1721, Walpole began to serve as Britain's first prime minister and would that position for the next 21 years. He was related to Walpole's leading ally, Charles Townshend, strengthening his bond with the leader of the new administration.