At six o'clock on May Day morning, the choir of Magdalen College, Oxford, ascend to the top of the College tower and there sing a Latin hymn, ‘Te Deum patrem colimus’. Meanwhile, in the streets below, thousands of onlookers have gathered for the event, including, nowadays, teams of morris dancers, jugglers, and other entertainers, and once the singing is over the church bells are rung, and a general street party ensues. The singing is documented since the late 18th century, but the other events have gradually developed since the 1920s. There are two main theories on the origin of the singing—one that it commemorates the building of the College tower (completed in 1509), the other that the custom started as an obit, or requiem mass for Henry VII (died 21 Apr. 1509).
Roy Judge, Folklore 97:1 (1986), 15–40;Shuel, 1985: 30–1.