In the 1980’s Furuta and Fintushel-Stern applied the theory of instantons and Chern-Simons invariants to develop a criterion for a collection of Seifert fibred homology spheres to be independent in the homology cobordism group of oriented homology 3-spheres. These results, together with some 4-dimensional constructions can be used to show that iterated Whitehead doubles of positive torus knots are independent in the smooth concordance group.