It might seem strange to associate a saint whose feast day falls even before the start of Advent with Christmas, and yet in the Middle Ages St Edmund was strongly linked to the Christmas celebration in a number of different ways. In the first place, St Edmund was often paired with St Nicholas of Myra (the Christmas saint par excellence), whose feast falls on 6 December. The reason for this pairing was that both saints were associated with the protection of seafarers. A second reason why St Edmund was associated with Christmas was the fact that his feast day inaugurated a fair in medieval Bury St Edmunds that lasted from 20 November until Christmas Eve. That fair has been revived in modern form, and still begins on St Edmund’s Day, although it no longer goes on until 24 December! In medieval Bury, therefore, St Edmund’s Day marked the start of preparations for Christmas, rather than Advent Sunday as elsewhere. St Edmund even had his own vernacular carol, which I recently adapted into modern English.
There are deeper reasons, however, for St Edmund’s links with Christmas. According to the Annals of St Neots, Edmund was crowned on Christmas Day 855 at a place called Burum (traditionally identified with Bures, near Sudbury). While this is almost certainly a later, fabricated tradition, Edmund did indeed become king of the East Angles in the mid-850s, and certainly by 860, judging from the numismatic evidence (which is the only contemporary evidence we have for Edmund’s actual reign). The practice of crowning kings on Christmas Day was quite widespread in the 9th century and went back to the coronation of Charlemagne in 800. A Christmas Day coronation underlined the king’s close relationship with Christ (whose kingship was especially emphasised in the Christmas liturgy), although 6 January was also a popular date, in order to elide a king with the magi/kings who came to worship the infant Christ. So it is certainly possible that the historical king Edmund really was inaugurated on Christmas Day, especially since his royal dynasty had a track record of appropriating imperial symbolism.
The final reason why Edmund became linked with Christmas in the Middle Ages was liturgical. The antiphon for first vespers of the Feast of St Edmund, Ave rex gentis Anglorum (‘Hail, king of the English people’) bears a superficial similarity to the Christmas antiphon Ave rex angelorum. The tradition of playing on the similarity of the Latin words for ‘angels’ and ‘English’ (angeli and Angli) is as old as the 6th century – Pope Gregory the Great famously did it – but the conflation of the two antiphons reached its apogee in 1433, when the young King Henry VI came to stay at St Edmunds Abbey for Christmas. The monks substituted the Christmas antiphon Ave rex angelorum for Ave rex gentis Anglorum, thereby not only substituting St Edmund for Christ but also substituting Henry VI for St Edmund, since the antiphon was effectively being sung to welcome the living king.
There is a curious coda to this story in an argument advanced by Prof. Bennett Zon that the 18th-century Christmas carol Adeste fideles (‘O Come All Ye Faithful’) plays on the same similarity between angeli and Angli. The carol was, according to Prof. Zon, a covert celebration of the birth of Prince Charles Edward Stuart (the Jacobite heir to the throne) on 20 December 1720. Curiously, at this period in the 18th century English Catholics erroneously celebrated the feast of St Edmund on 20 December, not 20 November, so it is possible the line natum videte regem angelorum (‘Come and behold him, born the king of angels’) was intended to reference St Edmund as well, whose ‘heavenly birthday’ was the day of his martyrdom. Or perhaps this is an interpretative leap too far…