The Celts started as a Central European Iron Age people, moving outwards to cover most of Europe, including the British Isles, by the third century BC. They were pushed westward by other cultures, particularly the Romans, and today Celtic culture is only found in Scotland, Ireland, Wales, Cornwall and Brittany.
Christianity was known to have come to the Celtic people by the second century AD and grew as an important form of Christianity in the British Isles till the sixth century - particularly after the Romans withdrew from Britain around 400 AD. Although it was never a unified body in the way the Roman church had become on continental Europe, it had a distinctive style - focussing on grace, creation and mysticism.
In 597 AD Augustine led a Roman mission to Britain. The Roman form of Christianity was by this time much more hierarchical, male and uniform with a strong form of governance. There were various disagreements between the Celtic and Roman 'camps' until the Synod of Whitby in 664 when Roman Christianity won the day over a number of issues - in particular the calculation of the date of Easter. After this time Celtic Christianity began to slowly wane in the British Isles and the Roman practices came much more to the fore, with Benedictine monasteries gradually replacing the older Celtic communities.
In the following centuries, the Celtic Christians became more localised and restricted. They were further pushed aside at the time of the Reformation, when suspicions were raised about past pagan influences on the Celtic forms of worship.
However, in the twentieth century interest was again sparked and new research into Celtic forms of spirituality began to grow. Some of what is now publicised as 'Celtic' is rather romanticised, but a new understanding has grown of the richness and vitality of Celtic spirituality and the legacy that it can pass on to us.
Well, enough of history! Here is a lovely blessing with a Celtic flavour from the Iona Community:
May the blessing of light be on you,
light without and light within.
May the blessed sunlight shine upon you and warm your heart
till it glows like a great fire
and strangers may warm themselves
as well as friends.
And may the light
shine from your eyes,
like a candle set in the window of a home,
bidding the wanderer to come in
out of the storm.
From 'An Iona Prayer Book' by Peter Millar