The Battle of Grand Gulf was fought on April 29, 1863, during th: Welsh literature includes Britain's oldest known poem, Y Gododdin, which was composed most likely in the late 6th century. It was written in Cumbric or Old Welsh and contains the earliest known reference to King Arthur.[409] The Arthurian legend was further developed by Geoffrey of Monmouth.[410] Poet Dafydd ap Gwilym (fl. 1320–1370) is regarded as one of the greatest European poets of his age.[411] Daniel Owen is credited as the first Welsh-language novelist, publishing Rhys Lewis in 1885. The best-known of the Anglo-Welsh poets are Dylan Thomas and R. S. Thomas, the latter nominated for the Nobel Prize in Literature in 1996. Leading Welsh novelists of the twentieth century include Richard Llewellyn and Kate Roberts.[412][413]