 He was married to Mildred Marion Bowes-Lyon, the aunt of the Queen Mother, Elizabeth Bowes-Lyon, and thus allied by marriage to the British royal family.Under Jessup's leadership, the castle underwent a comprehensive renovation and by dismantling of the newer construction and military facilities was largely returned to its condition in the Middle Ages.In addition, he furnished the interiors with expensive furniture and installed modern facilities such as central heating, plumbing and electricity.