The Monitor came about as a response to Specification Q9/42 for a twin-engined high-speed target tug for the Royal Air Force.

It was originally stipulated that the aircraft would incorporate the Bristol Beaufighter wing and landing gear to speed up design and production, but owing to increased demand for the Beaufighter only the landing gear was used, and a new all-wood one-piece wing was designed.

The aircraft was powered by two Wright Cyclone R-2600-31 radial engines driving Hamilton Standard Hydromatic propellers.

To meet this requirement the aircraft, fitted with hydraulically actuated dive brakes, nose cameras for marking Fleet gunnery, a dorsal midship cupola and radar equipment was used to accurately determine height[2] was known as the Monitor TT Mk II.

As with all aircraft for service use, the Monitor was evaluated by the Aeroplane and Armament Experimental Establishment (A&AEE) at RAF Boscombe Down.