Quote Originally Posted by Rob
Robbie,

The Welsh are not Gaelic. They come from the Brythonic branch of the Celtic peoples, along with the peoples of South West Scotland (Strathclyde), Southern England and Brittany.

Rob (A mostly Brythonic Celt)
In general this is right, however, to complicate matters considerably, there has been a long and constant settlement of Irish in parts of Wales.

The Llyn Peninsula and the neighbouring parts of Gwynedd and Meirionydd have a lot of Irish 'blood', as have parts of Pembrokeshire and also the Gower Peninsula and Swansea (these latter were settled at one time - before the coming of the Northmen from Limerick (hence Swansea - Svegnes Nes) - by an Irish clan called the Ui Leathain, who may have been some of the Deisi on the run). Also, there's quite a lot of Welsh (Brythonic?) settlement in the area of Cork.

This is also true of the Cornish Peninsula (which probably should include Devon and Somerset), and Brittany. There is also evidence of Irish settling in Galicia in historic time.

St Asaph and some other foundations nearby on the northern coast of Gwynedd were tributary houses associated with Saints Moluag and Mungo - in the latter case Lothian, and therefore Brythonic, but in the case of the former certainly Gaelic.

The north-west of England from the Welsh border to the Scottish border were Welsh speaking areas at the time of the coming of the Northmen - hence Cumbria, which once described the whole area - and, if we take what has happened in west and north-west Wales as an indication, almost certainly shared the cross-settlement with Ireland, Man, and Galloway (and thus Gaelic-ness).

So we should probably be cautious about drawing hard-and-fast conclusions about the Western Insular and Continental Celts. And given the patterns of cross-settlement and mixing of populations, it's going to be a fair bet that Welsh, Cornish, Bretons, and Gallegos would be able to put up a passable claim to sharing in the Irish/Scots heritage - and probably vice versa.