The Marquesses of Bute acquired the castle in 1776. John Stuart, the first marquess, took steps to protect the ruins. His great-grandson John Crichton-Stuart, the third marquess, was immensely rich as the result of the family's holdings in the South Wales coalfields and was passionately interested in the medieval period. He had the site fully surveyed by the architect William Frame, and reroofed the great hall in the 1870s. The marquess began a process of buying back leasehold properties around the castle with the intent of clearing back the town houses that had been built up to the edge of the site.