Work on a more advanced armoured fighter, conceived as an armoured version of the Sopwith Snipe, began early in 1918. The forward portion of the fuselage was a 605 lb (275 kg) box of armour plate, forming an integral part of the aircraft structure, protecting the pilot and fuel system, with a 0.315 in (8 mm) front plate, a 0.433 in (11 mm) bottom plate, 0.236 in (6 mm) side plates and rear armour consisting of an 11-gauge and 6-gauge plate separated by an air gap. The rear (unarmoured) section of the fuselage was a generally similar structure to the Snipe but flat sided, to match the forepart. The two-bay wings and tailplane were identical in form to those of the Snipe but were strengthened to cope with the extra weight, while the fin and rudder were identical to the Snipe. The new aircraft used the same Bentley BR2 rotary engine as the Snipe, covered by an unarmoured cowling – the foremost armour plate forming the firewall.