The medal has on occasion been awarded to multiple people at a time; in 1938 it was won by John Cockcroft and Ernest Walton "for their discovery that nuclei could be disintegrated by artificially produced bombarding particles", in 1981 by Peter Higgs and Tom Kibble "for their international contributions about the spontaneous breaking of fundamental symmetries in elementary-particle theory", in 1982 by Drummond Matthews and Frederick Vine "for their elucidation of the magnetic properties of the ocean floors which subsequently led to the plate tectonic hypothesis" and in 1988 by Archibald Howie and M. J. Whelan "for their contributions to the theory of electron diffraction and microscopy, and its application to the study of lattice defects in crystals".