Edge-colouring eight-regular planar graphs

It was conjectured by the third author in about 1973 that every d-regular planar graph (possibly with parallel edges) can be d-edge-coloured, provided that for every odd set X of vertices, there are at least d edges between X   and its complement. For d=3d=3 this is the four-colour theorem, and the conjecture has been proved for all d≤7d≤7, by various authors. Here we prove it for d=8d=8.