In the late 1950s, Richards discovered one of his best-known themes, the legend of the submerged cathedral, said to lie off the coast of Brittany near Ys, La Cathedrale Engloutie. The legend had also previously inspired Debussy's prelude of the same title. Richards who played the piano for pleasure and the inspiration it brought, painted his notions of the legend on a series of large and small canvases. Richards' response to Debussy's music and his feeling of the coastal seascape and weather was rekindled on the Gower peninsular in Wales.
On mornings of spatial calmness and clarity the cathedral was said to rise out of the deep, it's bells ringing and it's priests chanting, then slowly return to the depths and enchanted sleep. Alan Bowness comments, 'the associations aroused by Debussy's music become more and more powerful ... fragments of the cathedral itself, washed by the relentless movements of the sea, fill the pictures. Looking down into the greeny-blue waters one can discern rose-windows or arches filled with flowering tracery or the great round piers that seem to echo from the depths like Debussy's saturated chords' (see J. Webster, (intro.), Exhibition catalogue, Ceri Richards, Welsh Committee of the Arts Council of Great Britain, 1961, p. 8).