Ronald Hutton doesn't know. Ronald Hutton is the scholar who wrote a splendid debunking book in 1996 called The Stations of the Sun. What he debunked was the old nonsense dreamed up by anti-Christian students of 'Comparative Religion' in the first half of the twentieth century, led by Sir James Frazer. Those people enjoyed 'showing' that most Christian festivals were ancient pagan festivals very thinly disguised, and that Christianity so failed to leave its mark deep in the psyche of the common folk of the British Isles that many pagan rites survived the official triumph of the Galilaean Faith. An example:
At Padstow in Cornwall, two hobby-horses dance their way through the town each May Day. In the 1930s some daft people called the Folk-Lore Society persuaded themselves that this was a relic of a pagan sacred marriage between Earth and Sky. (Hutton gives a witty and hilarious account of the antics of one of these nutters, called Violet Alford.) The town council cheerfully assured prospective tourists that it was a Celtic custom 4,000 years old. But modern scholarship, Hutton demonstrates, shows that there is no evidence for the custom going back beyond the late eighteenth century and very good reasons for being confident that it did not.
At the beginning of August, in many parts of Ireland, the country people climbed mountains and indulged in bonfires and jollity in honour of the God Lugh. Hutton, however, the spoil sport, gives good reasons for doubting whether these customs really have anything at all to do with the 'Celtic' god Lugh. They celebrated the opening of the cereal or potato harvest. And, as such, they were broadly parallel with the Anglo-Saxon celebration of 'hlaef-mass', loafmass, Lammas. It was the custom to reap the first of the ripe cereals and bake them into bread which was blessed in church upon that day; quaint things were sometimes then done to it to make the barns into safe repositories for the grain about to arrive in them.
Hutton leaves it an open question whether there is a direct link beteween the Lammas ceremonies and those of Lughnasa. But he does see both as "a reminder of the excitement which once attended the ripening of the corn across the ancient British Isles" (the 'Atlantic Archipelago', for my Irish readers).
But in S Thomas's we won't be doing any jiggery pokery onLammas Day, August 1; we shall simply be celebrating S Peter ad vincula, S Peter's chains, the commemoration of the Dedication of the Roman Basilica of the Apostles which, since the deposition within it of a relic of the chains which confined S Peter in his prison, has had the popular name of S Peter ad Vincula. (Just like the chapel in the Tower of London, final resting place of a number of of unfortunates who never made it out. Perhaps we should remember them too at Saturday's Mass.)