He rebuilt Petworth House in Sussex, the ancient Percy seat inherited from his wife, in the palatial form which survives today.

According to the Encyclopædia Britannica Eleventh Edition, he was a remarkably handsome man, and inordinately fond of taking a conspicuous part in court ceremonial; his vanity, which earned him the sobriquet of "the proud duke", was a byword among his contemporaries and was the subject of numerous anecdotes; Macaulay described him as "a man in whom the pride of birth and rank amounted almost to a disease".

However, the 5th Duke did not inherit the unentailed Seymour estates, including the family seat of Wulfhall and other Wiltshire estates, and much of the lands of the feudal barony of Hatch Beauchamp in Somerset, which were bequeathed to the 4th duke's niece, Elizabeth Seymour, wife of Thomas Bruce, 2nd Earl of Ailesbury (1656–1741).

Three years later, in 1678, Charles's brother, the 5th duke, was murdered in Italy, aged 20, unmarried and without progeny, having been shot at the door of his inn at Lerici.

A painting made in about 1700 of his new house was identified by the art historian Sir Anthony Blunt in the collection of the Duke of Rutland at Belvoir Castle.

Today the roofline is lower and flat, giving the building a plain appearance, possibly following the fire of 1714 and subsequent repairs.

[10][a] However, he fell from favour in 1687 when as Lord of the Bedchamber he refused to escort the newly appointed Papal Nuncio and was deprived of his various offices.

[1] The Duchess of Somerset became the Queen's closest confidante, causing Jonathan Swift to direct at her a violent satire, The Windsor Prophecy, in which he accused her of murdering her previous husband, Thomas Thynne (died 1682)[12] of Longleat.

[1] He retained the office of Master of the Horse for the first year of the reign of King George I (1714–1727) until 1715,[14] when he was dismissed and retired to private life.

He treated her poorly and once told her, after she had gently tapped him on the shoulder with her fan: "Madam, my first wife was a Percy and she never took such a liberty".

[18] By Charlotte Finch he had two further children: Somerset's last known letter to Sarah Churchill, Duchess of Marlborough, dated 1737, twelve years after his second marriage, declared his unchanged affections for her.

It was deemed appropriate and necessary by all parties concerned, including the King, that heirs to such families and estates as the Percys and Seymours should be elevated to the peerage.