Herstmonceux Castle, East Sussex, 1920s. View of the ivy-clad entrance gatehouse. Herstmonceux Castle was built of brick c1445 by Sir Roger Fiennes. It was largely dismantled in 1777 and remained an ivy-clad ruin until the early 20th century when a major restoration programme was carried out. It housed the Royal Observatory for a time in the late 20th century.