Phos Hilaron (Φῶς Ἱλαρόν) is an ancient Christian hymn originally written in New Testament Greek. Often referred to by its Latin title Lumen Hilare it has been translated into English as 'Hail Gladdening Light' or 'O Gladsome/Joyous Light'. It is the earliest known Christian hymn recorded outside of the Bible that is still in use today. This composition by Andrew Walker uses an English version of the words from the 1979 BCP (US) Evensong Rite 1 and was first published in 1986