the Heinkel's elliptical wing is credited with being the source of the Spitfire's elegant planform
You see the claim oft made, but not really credible when you read the development steps of the wing. Best illustrated by the following scans. Mitchell had used the elliptical wing as early as July 1929 on a six engined flying boat designed to meet Air Ministry Specification 20/28 which had been issued in January 1929.
Beverley Shenstone, RJ Mitchell's aerodynamic advisor denied that the Spitfire wing was copied from the He 70. Shenstone said:
It has been suggested that we at Supermarine had cribbed the wing shape from that of the He 70 transport. This was not so. The elliptical wing had been used on other aircraft and its advantages were well known. Our wing was much thinner than that of the Heinkel and had a quite different section. In any case it would have been simply asking for trouble to have copied a wing shape from an aircraft designed for an entirely different purpose.
Shenstone said that the He 70's influence on the Spitfire design was limited to use as a benchmark for aerodynamic smoothness.