On deployment we worked with QRF soldiers from Glasgow. I could barely understand them. One guy literally sounded like “Oy oh guh [f-bomb] uh toy uh [f-bomb] ut oy eya uh..” all I could understand were the numerous f-bombs. Great soldiers, but just couldn’t understand them.
Same with the Irish, at least the ones I met back in the ‘80s. I dated one, but I could barely understand a word he said, except for the numerous f-bombs.