Although not strictly a Martello tower, Bréhon represents the final evolution of the basic design of the Martello tower. In 1914 the War Office transferred ownership of Bréhon Tower to the States of Guernsey. During the German occupation of the Channel Islands, the German military placed anti-aircraft guns on the tower. Today, although the site is open to visitors, the tower is closed. The tower holds a light operated by the Guernsey Harbour Authority. The island is home to a breeding colony of common terns.