Supermarine Spitfire Mk IV
The Supermarine Spitfire Mk IV was a development aircraft installing the Rolls Royce Griffin in the Spitfire for the first time. Spitfire DP845 was used as the development airframe. The primary difference to the merlin powered models, was the cowling modifications to accommodate the new engine, larger radiator air intakes and a larger tail. A mockup with six 20 mm cannon was produced, but this armament was never used.
To avoid confusion with the PR. Mk IV, the model was re-named Mk XX, and then produced as the Mk XII.
