Original: This version was capable of a maximum speed of 342 mph, some 25 to 30 mph faster than the Mk I/O. The performance of the Spitfire over Dunkirk came as a surprise to the Jagdwaffe, although the German pilots retained a strong belief that the 109 was the superior fighter.
Simplified: This version was capable of a maximum speed of 342 mph, some 25 to 30 mph faster than the Mk I.