In the Mabinogion tale of Lludd and Llefelys, which seems heavily influenced by Geoffrey of Monmouth's work, he is the ruler of Britain while his brother Llefelys ruled Gaul.
The name of Ljot is very close to that of Lot or Loth, the mythic King of Orkney and Lothian in Arthurian legend, and in Celtic Myths and Legends (1912), Charles Squire identifies Lot as a late incarnation of a British god who is remembered in medieval Welsh legend as Lludd Llaw Eraint.