Create a world where the English were able to Conquer the Irish Empire instead of the other way around. I would say having the Romans colonize England instead of Ireland might have been a good start.
OOC: This thread! щ(゚Д゚щ) They were only dimly aware (if aware at all) of Hibernia's existence, and Britannia was well known for its tin. There would be little benefit in conquering Ireland, except to prevent pirate raids on Britannia, but with no Roman Britannia...I would say having the Romans colonize England instead of Ireland might have been a good start.
OOC: This thread! щ(゚Д゚щ) They were only dimly aware (if aware at all) of Hibernia's existence, and Britannia was well known for its tin. There would be little benefit in conquering Ireland, except to prevent pirate raids on Britannia, but with no Roman Britannia...
A better POD might be the complete conquest of the british isles, and the introduction of then-modern agricultural methods and market towns to Roman Hibernia, so while Britain suffers the germanic invasions, Hibernia is relatively prosperous.