Guy de Brian's death in 1390 was followed by a long period of decline and in the late 15th and early 16th century only parts of the castle were occupied. However, a real change came about in the castle's fortunes when, in 1575, Elizabeth I granted it to Sir John Perrot, an important dignitary who converted the old medieval castle into a comfortable Tudor mansion. Unfortunately for the castle, Perrot became too powerful for Royal comfort, and in 1592 he was sentenced to death for high treason; he died, though from natural causes, in the same year.