I built a Red Arrows G.91 (but mucked up the paint) based on the idea that the RAF bought into the standard NATO attack aircraft idea.
The idea was that most of NATO bought into the G.91, but that the unity fell apart in the next generation, with the RAF and Luftwaffe going with the Harrier, the Italians the G.91Y (rejected by the rest because of it's American engines), and most of the export customers swapping to the F-5E. That left the next generation trainer requirement to sort out: Shorts and Breguet came up with an Adour-engined G.91T rebuild, and that took the place occupied in the real world by the Hawk and the Alpha Jet.