Remarks by Ed Jones: "This aircraft (J9933) was built as a Hart but used as the prototype for the Hawker Demon and later fitted with the Frazer-Nash gun turret with the 'lobster-back' or 'turtle-back' folding shield as shown in the photo. The original Demon had an inclined Scarff ring mounting like the later Hawker biplane light bombers (Osprey, etc.).
J9933 has the long exhaust pipe to limit exhaust flame. Reason for the 'lobster-back' was to protect the gunner from the slipstream when aiming on the beam. It was better than some of the single seat fighters of the day (1933) and was the origin of the turret fighter concept which lead to the Boulton Paul Defiant.