By the end of the sailing era the 50-gun ship had become regarded as a hybrid, too small to stand in the line of battle, and lacking the speed and hardiness of the frigate, so it has often been dismissed as a naval architectural dinosaur left over from an earlier age. This book aims to reveal the crucial role of the 50-gun ship in the development of both the battleship and the frigate, and explains the enduring role which ensured the survival of the type into the 19th century. Charting its origins in the pre-Commonwealth frigates, the author follows the development of the type in the 18th century and its gradual transition from battlefleet to heavy cruiser role, highlighting its revival for the special conditions of colonial warfare during the American Revolution. Thereafter they were employed as peacetime flagships for distant stations, achieving final glory leading small craft in anti-invasion operations during the Napoleonic War. The Leopard is the subject of the cutaway drawings.