I suppose a better answer would be that the Rootes Group was a hodgepodge of car makers and designers that made short runs of variations of their typical models to appeal to car enthusiasts. They used a lot of different parts from different car companies. The 4 cylinder engine in my car was designed by Ferrari and there was a stamp in the door sill that said Ferrari Coach Works. That didn't mean that the car was built by Ferrari, by the Rootes Group folks hoped the involvement with Ferrari would booster sales (as I understand it). If you delve into British sports cars, you may find just about anything.