Grafton (1735-1811) was in charge for much of Chatham’s last administration, giving him three years (1767-70) in effective power, although part of this was occupied in obtaining a divorce by Act of Parliament, which he did in 1769 (more of an intellectual than a rake, he then settled down with a clergyman’s daughter to a long and happy second marriage). He was also distracted by supervising his racing stable and his estates.
He was made Secretary of State for the Northern Department at 29 by Rockingham, then resigned from his government and joined Pitt in a new administration which at the King’s wish included a few Bute Tories including North and (in a junior office) Charles Jenkinson. He was a conciliator of the American colonies, but when he opposed the American secretary Hillsborough’s coercive measures in 1769 he was outvoted in his own Cabinet.
Overall, Grafton was somewhat ineffective, certainly in conciliating the American colonists, but probably deserves to rank a little above the dregs..