By the beginning of 1941, the War Office had issued four specifications for military gliders to be used by the airborne forces. The first was Air Ministry specification X.10/40, which called for an eight-seater glider similar to the German DFS 230, which eventually became the General Aircraft Hotspur I; the second was specification X.25/40 which became the Slingsby Hengist, a fifteen-seat glider; the third was specification X.26/40, the 25-seater Airspeed Horsa; and the last, X.27/40 was for a glider that could carry a light tank or other heavy loads. The number of aeronautical firms able to design and produce gliders was limited, especially since several were already committed to producing other prop-driven aircraft for the government; as such, contracts for the gliders were allocated to firms as the government saw fit, rather than through any competitive process. Slingsby was chosen to develop "X.25/40" because it was believed to be too small to build larger gliders, and Airspeed would eventually build the Horsa. Because it had already developed the Hotspur, which first flew in November 1940, and was considered to have a sufficiently developed production capacity capable of producing a larger glider, General Aircraft Limited were chosen to develop X.27/40. Before being selected, the company had already been in the process of developing designs for a glider which would carry a single Mk VII 'Tetrarch' light tank. The design was a low-wing aircraft designed so that the tank driver also functioned as the glider pilot, and flew the glider from his seat in the tank through a series of internal modifications to the tank. The idea behind the design was to save on specially-trained glider pilots and allow the tank to be brought into action as soon as the glider landed; surviving illustrations of the design show the tank encased in the glider's fuselage but with the turret outside the airframe, possibly so that it could engage targets as it landed. However, the design was considered to be impractical, both by the company and the War Office, and a more conventional design was finally arrived at in a joint meeting between the two in January 1941. It called for a glider which would be constructed primarily out of wood capable of carrying a Tetrarch light tank and two Universal Carriers with a combined maximum weight of approximately ; a surviving requisition form from the Air Ministry to GAL confirms a cost of £50,000 per glider.