The memory of Llewelyn Williams was honoured on 1 July 1937, when members of the Carmarthenshire Antiquarian Society visited his birthplace and his grave, an occasion during which it was recalled that he was largely instrumental in bringing about the Royal Commission on Ancient Monuments in Wales and Monmouthshire, set up in 1908. In the year following the society's visit, a commemorative plaque was unveiled at Brownhill.