ORIGINAL: Not24
It is a known fact that the elliptical wing planform, as on a spitfire, gives the best spanwise lift distribution, and thus, the most efficient wing design as relating to overall lift and drag performance.
In the second half of WWII, UK Spitfire pilots used to cut off about 18" off each wingtip, and gave the Spitfire a flat edge to each wing tip. They did this to improve roll rate.
As the war progressed, and especially after the Normandy invasions, the role of the Spitfire changed from Air to Air Fighter, to Ground Attack. They wanted the increased roll rate for low level flying, and were willing to accept a lower ceiling that followed from the lower efficiency from the wing.