I missed this at the weekend:
https://www.theguardian.com/science/2025/mar/08/celtic-languages-ireland
Interesting
I must admit that when I read " a global climate event caused western Europe to become very wet. McLaughlin thinks that associated disasters such as crop failures or epidemics triggered an Irish "brain drain" to Britain."
I wonder if this was one of the reasons why the Irish moved to pastoral agriculture and cattle.
The fact that Ireland is wetter than England anyway, Also less sunshine means you aren't going to get the quality of breadmaking wheats. To quote the wiki "A major livestock producer, Ireland has very limited horticultural and grain production on account of its topography and climate."
The main native grains were oats and barley and bread made from wheat was considered a luxury. It's an interesting article: I hadn't heard of the "refugees from Rome" theory: it might explain the existence of some population groups with apparently British names (Fir Domhnann = Dumnonii) but then others like the Manapii of Ptolemy's map have been associated with Gallic tribal names and a direct Gaul to Ireland migration is unlikely. I confess a 1st century AD date seems very late to me but I'm not a linguist.