1. A method of optimising the design of a component, in which method a set of principal design variants is generated, the principal design variants having design parameters which are common to all principal design variants of the set and having design variables which differ between the principal design variants of the set, the method further comprising generating at least one secondary design variant from at least one of the principal design variants by modifying at least one of the design parameters or the design variants of the at least one principal design variant.