T. W. Clyne is Professor of Mechanics of Materials in the Department of Materials Science and Metallurgy at the University of Cambridge, and the Director of the Gordon Laboratory. He is also the Director of DoITPoMS, an educational materials science website, a Fellow of the Royal Academy of Engineering, and a Helmholtz International Fellow. J. E. Campbell is Chief Engineer at Plastometrex (PhD University of Cambridge) with expertise in mechanical testing of metals with a focus on indentation and finite element modelling.