 Having been on active service for the best part of two years, he successfully applied to the Canadian War Records Office for a commission to paint a large-scale war subject.In April 1918 he returned to London as an official war artist, with the proviso that the work should not be in the Cubist style.The outcome of the commission was "The First German Gas Attack at Ypres", a powerful expressionist work that is on permanent display in the Canadian War Museum in Ottawa.