Complex sentence: As a senior member of the Rockingham faction of the Whigs, he opposed the King's legal actions against the reformist John Wilkes in 1763 which resulted in his dismissal in 1764 as a Groom of the Bedchamber and as Colonel of the 1st Royal Dragoons.
Split into simpler sentences: As a senior member of the Rockingham faction of the Whigs, he opposed the King's legal actions against the reformist John Wilkes in 1763. This resulted in his dismissal as a Groom of the Bedchamber and as Colonel of the 1st Royal Dragoons.