Penhow Castle was built as a home for Sir Roger de Sancto Mauro, one of the Norman knights who served the Norman Lord of Striguil at Chepstow Castle. He built a tower house, and documentary evidence shows that he was at Penhow by 1129.
It was the first British home of the family who would later rise to national prominence under the more familiar name of Seymour. Later the Seymour family sold Penhow Castle to the Lewis family of St. Pierre, who converted the castle to a modern residence in 1674. Thomas Lewis’ son Thomas was High Sheriff of the county, and married the daughter of Sir Richard Levett, Lord Mayor of London. The Lewis’ retained ownership of Penhow Castle for several centuries. The castle has a reputation for being haunted. It was open to the public between 1978 and 2002.