[1] Originally the site of a fortified manor house with licence to crenellate in 1332, the manor of Mereworth was inherited by Francis Fane, 1st Earl of Westmorland (1580-1629) (son and heir of Sir Thomas Fane (died 1589) of Badsell in the parish of Tudeley in Kent) from his mother Mary Neville, suo jure Baroness le Despenser (c. 1554–1626),[2] sole daughter and heiress of Henry Nevill, 6th Baron Bergavenny (died 1587).

The present building is not actually a castle, but was built in the 1720s by John Fane, 7th Earl of Westmorland[3] to the 1723 design of the architect Colen Campbell being an almost exact copy of Palladio's Villa Rotunda near Venice.

[4] The interior features plasterwork by Giovanni Bagutti and fresco painting by Francesco Sleter.

The house is situated in a landscaped park and valley with a number of surrounding pavilions and lodges which are also Grade I listed.

[8] In the 1950s and 1960s it was owned by artist Michael Lambert Tree (1921–1999[9]), a son of Ronald Tree and an heir to the Marshall Field mercantile fortune, and his wife, Lady Anne Cavendish, daughter of the 10th Duke of Devonshire.