In 1963, BAC Warton was working on the preliminary design of a two-seat Lightning development with a variable-geometry wing, based on the Lightning T.5. In addition to the variable-sweep wing, which was to sweepback between 25 degrees and 60 degrees, the proposed design featured an extended ventral pack for greater fuel capacity, an enlarged dorsal fin fairing, an arrestor hook, and a revised inward-retracting undercarriage. The aircraft was designed to be compatible with the Royal Navy's existing aircraft carriers carrier-based aircraft, the VG Lightning concept was revised into a land-based interceptor intended for the RAF the following year. Various alternative engines to the Avon were suggested, such as the newer Rolls-Royce Spey engine. It is likely that the VG Lightning would have adopted a solid nose (by moving the air inlet to the sides or to upper fuselage) to install a larger, more capable radar.