Born in London in 1928 the son of Irish dramatist Sean O'Casey.
He attended Dartington Hall School and was taught metalwork by ex-Bauhaus teacher Naum Slutski. After studying at the Anglo French Art Centre Breon moved to St Ives becoming assistant to sculptors Denis Mitchell and Barbara Hepworth.
Despite huge success as a jeweller, Breon considered himself primarily a painter and he discovered his talent for sculpture during the last two decades of his life which provided him with a working equilibrium.
The larger proportion of Breon's paintings and prints are abstract and his sculpture falls into three categories: the figure, animals and birds.