 As a painter, his style changed over time from more free water colour landscapes, still lifes, and portraits to a unique mixture of pencil and water colour resulting in dense and busy works full of symbolism.His best-known paintings include early seascapes such as "Manawydan's Glass Door" and later works on legendary subjects, such as "Trystan ac Esyllt" (Tristan and Iseult).He is also much admired for a genre that he invented later in life, which he termed "painted inscriptions", and these exert a continuing influence on calligraphers.