Thought I'd better get involved as I've had so many calls about this.
The original version was written in,I think,1970.
The Hennessys had returned from a year in Ireland and had become quite heavily involved in the Welsh language folk scene back home.
The Welsh writer and TV Director Rhydderch Jones took us on a "cultural" tour of Wales, which involved a visit to the Priory Oak.
At this time the old stump still stood in it's original spot in the middle of the road going into Carmarthen.
Rhydderch told me the story about Merlin planting the acorn and casting a spell over it.
The prophecy went " If the old oak tree shall 'ere come down - then will drown Carmarthen Town".
My chorus was half written for me and the rest of the song came fairly quickly.
Rhydderch wrote a Welsh version which was an immediate success and it was not long before the song became accepted in Wales as a bilingual standard.
I'd had a big hit in Ireland the previous year with another song, called "The Gypsy", and the Irish wanted a follow up.
Almost in jest I suggested that Dungarvan, which is where my paternal family came from, sounded very much like Carmarthen.
Two months later I had my second Irish number one and the first Dual-nationality contemporary folk song was born.
In the early days I had trouble convincing people that the song was contemporary and not traditional, but over the years this little ditty, in all its forms has become central to my musical life, and I'm glad to say, is much loved by both the people of Wales and Ireland.
And yes, you are right! Brethin is a rough, home-spun Welsh cloth, whereas Brecon is a rather refined Welsh market/garrison town.
Thanks to everyone for their interest, and thanks for listening to Celtic Heartbeat on BBC Radio Wales each Saturday night at ten.
Good luck to you all,
Hwyl fawr i chi gyd,