The hardest movie for me to understand was probably
Quadrophenia,
years ago. I couldn't tell what anyone was saying. I do usually have a problem with Guy Ritchie movies, though.
Snatch
was really hard to understand.
My problem lately is the conflict between soundtrack and dialogue. The music is usually too loud to hear the dialogue right, somehow.
I want the Shoes & Tim Roth. Who, BTW, was tweeting all kinds of backstage pics from the rehearsal & show.
I recall watching a British indie gay comedy a few years ago that really needed subtitles for American English speakers. The Irish leads might as well have been speaking Gaelic for all I could tell, and I don't normally have trouble following Irish accents.
I"m not very good with accents--cf mine own. So it's perfectly possible Downey was in my sweet spot of ni America ni Britain, but whatever he was, I could hear the words. I think it's two things, neither of which applied to me watching.
Northern Ireland Irish?
I don't know, but I'd hear about one distinct consonant for every couple minutes of talking. It sounded like someone communicating while gargling. Or John Mayer singing.
Just wondering about a British movie with Irish leads. Not that it can't happen, but it seems to open it up for more accent shenanigans.
Not all of the leads were Irish, but the main character of The Crying Game was. And I could understand everyone in that movie.