Lud's reign is notable for the building of cities and the refortification of Trinovantum (London), which he especially loved. Geoffrey explained the name "London" as deriving from "Caer Lud", or Lud's Fortress. When he died, he was buried at Ludgate. His two sons, Androgeus and Tenvantius, were not yet of age, so he was succeeded by his brother Cassibelanus.
In the Welsh versions of Geoffrey's Historia, usually called Brut y Brenhinedd, he is called Lludd fab Beli. An independent Welsh tale, Cyfranc Lludd a Llefelys ("The Tale of Lludd and Llefelys"), one of the tales now known as the Mabinogion, is included in one Welsh version of the Historia. While Lludd was king of the Island of Britain, his brother Llefelys (not found in Geoffrey's work) became king of France, and helped Lludd to rid Britain of three supernatural menaces. He may be connected with the Welsh mythological figure Lludd Llaw Eraint, earlier Nudd Llaw Eraint, cognate with the Irish Nuada Airgetlám, a king of the Tuatha Dé Danann. However, he was a separate figure in Welsh tradition and is usually treated as such.
Numerous toponyms in England and one in Ireland (Ludden, Limerick) are based on Lud-, Ludden-, Luddes-, or Ludger-. The toponyms range as far north as County Durham, and as far west as Ludgvan, Somerset, but only two are to be found in Wales, Luford, Herefordshire, and Ludchurch, Permbrokeshire.