Saint Elen, often anglicized as Helen, was a late 4th-century founder of churches in Wales. Traditionally, she is said to have been a daughter of the Romano-British ruler Octavius / Eudaf Hen and the wife of Magnus Maximus / Macsen Wledig, the 4th-century emperor in Britain, Gaul, and Spain who was killed in battle in 388. Although never formally canonized by Rome, Elen is traditionally considered a saint in the Welsh Church; in English she is sometimes known as Saint Helen of Caernarfon to distinguish her from Saint Helena.

Conan Meriadoc is a legendary British Celtic leader credited with founding Brittany. Versions of his story circulated in both Brittany and Great Britain from at least the early 12th century, and supplanted earlier legends of Brittany's foundation. His story is known in two major versions, which appear in the Welsh text known as The Dream of Macsen Wledig, and in Geoffrey of Monmouth's Historia Regum Britanniae. Both texts associate him with Magnus Maximus, a Roman usurper against the Valentinianic dynasty who was widely regarded as having deprived Britain of its defences when he took its legions to claim the imperial throne. Conan's cousin or sister, Saint Elen, is said to have been Macsen Wledic's wife.