The great folk song of 'The Ould Lammas Fair of Ballycastle O' is a celebration of one of the oldest and most popular fairs in Ireland. It still has the power to draw visitors from far and wide and is a not-to-be-missed event for the locals. It is full of history. For older folks, it is a time to remember 'the scene that haunt' the memories. For the younger folk, it is an occasion to tune into the excitement of a by-gone times. - When else would one enjoy the unsophisticated taste of dulse and yellow-man except, of course, when - like in the song - on the pouting lips of a Mary-Anne. But the ancient reach of the Lammas Fair goes much further. Its origins are immersed in pre-history, in times long before the message of St Patrick was heard in Ireland, when gods of light and fertility were celebrated. This booklet, an updated publication of the original written in the 1966, retraces much of what is known and some of what can only be guessed at about the origin and development of this truly traditional event.