The minimum degree of minimal Ramsey graphs for cliques

We prove that (Formula presented.), where (Formula presented.) is the Ramsey parameter introduced by Burr, Erdős and Lovász in 1976, which is defined as the smallest minimum degree of a graph (Formula presented.) such that any (Formula presented.) -colouring of the edges of (Formula presented.) contains a monochromatic (Formula presented.), whereas no proper subgraph of (Formula presented.) has this property. The construction used in our proof relies on a group theoretic model of generalised quadrangles introduced by Kantor in 1980.