The film is outstanding in its portrayal of a "man who loved too much" going psycho and then pulling back.
The language is extreme but given a stylised almost poetic rhythm; great nods here to David Mamet and his stylised approach to dialogue.
As others have said it feels very much like a stage play in its claustrophobic 5(+1 in hood) men in a room talking heads approach; and if you're after the usual car chases, blood and guts and trite ending this is not for you.
The characters are, I think, ciphers for different aspects of Ray's character, Colin Diamond's mind
John Hurt's old man peanut is a vicious misogynist, angry about everything
Steven Dillane as Mal, violent without conscience, wanting an eye for an eye
Tom Wilkinson as Archie, loyal, loves his mum and wants life long commitment
Ian McShane's Meredith, the cold intellectual. Who never loves, with sex being an act not an emotion. His gayness perhaps being used to convey Colin's feeling of loss of masculinity because of his wife's infidelity.
These characters are used to get Colin to face his dilemma and decide on revenge (on the hooded & cuffed perpetrator in the corner) or acceptance that he has lost, and let the perpetrator go .
The other characters, Joanne Whalley as the wife and a weirdly OTT cameo from Steven Berkoff are seen in flashback to fill out the back story.
I was gripped by this well acted film from start to finish and as I ejected the blu ray from the machine was left with the question, was any of it real, or was this all played out in Colin's mind in the drunken aftermath of his wife saying "I've met someone else"...I don't know but I'm glad the film made me think something!