The 'official' blurb kinda tells the tale, but I would have said it thus: two London Eastend gobshites acquire a lump of 'hot' (meaning a chattel to which they do not have absolutely clear title of ownership) uranium and decide to 'monetize' it, as our yank cousins would put it.
First they approach Colin Meany's character, the local heavy, Harry - a role just made for Colm! - who takes them to 'the twins' - obviously you should read the psycho 'Cray Bros.' here - after which we meet a succession of weird and wonderful con artists, villains, bullies and a really spooky CIA spook.
And all the time the characters' domestic arrangements are moving ahead, complexifying the action and putting additional demands on the characters.
The action is full of novel ideas and twists and turns, yet never inconsistent - the storyline is well served by script and actors. Worthy of remark is the cinematography in so many European city locations, as well as out in the bush.
Overall it's just a fabulous film, the only way to lose interest during this is to die (laughing or otherwise) during the show. As another commentator remarked, it is not full of the foulmouthedness so usual today, and I must also remark that - unlike Hollywood - it did not leave a death toll to compare with Dachau, as most yank 'entertainments' do.
Buy it, rent it, pirate it - just don't miss it!