Story of a charming man

Yet the moment the Hollywood bruiser bounds in with a cheery 'hullo!' and a bounce of his mane, I am completely disarmed. Warm, jokey and teddy-tubby in a red fleece, he resembles less the surly Gladiator, more a slightly gone to seed Cowardly Lion.

And he's rightly roaring with pride about American Gangster, a 1970s Harlem-set true-crime story in which he stars as Richie Roberts, the ethical cop with a messy personal life who brings down famed drug dealer and crime lord Frank Lucas (Denzel Washington).

'I really wanted to play Lucas,' says Crowe, 'so when I read the script I repaid the loyalty Denzel had shown me 12 years earlier.'

Washington, now a firm 'mate', had got him a role in Virtuosity, a 1995 sci-fi flick. 'I was having a helluva lot of fun playing an artificial, computer-generated serial killer, as you do, and at one point Denzel turned to me and said, "Man, I wish I was playing your role." It's why I thought of him for this.'

Aside from the obvious fact that Lucas is black, Crowe is far more suited to playing Richie, the bullish, antisocial detective who fits the actor's trademark hard-boiled, softcentred MO as well as his tabloid image. As the Oscar-winning LA Confidential star is all too aware.

'Richie is a very humble and reticent man,' he says of his meeting with the real man. 'Talking to him was quite difficult. I'd ask a very complicated question and get a one-word answer. Similar to how journalists feel about me, no doubt...'

Not today. Earthily foul-mouthed and a natural storyteller, Crowe is clearly relishing having a captive audience, regaling me with chatty anecdotes ('The scene had just started, the camera's on me, and I realise I've just spat on Denzel Washington...') sugared with home insights: 'At this point, my son's nearly four and he thinks a box of sultanas is the greatest thing God ever sent to Earth. If I can keep him in a place where simple things give him great pleasure, that will be a great advantage to both of us.'

That said, Crowe, probably wisely, sees any conversation with a representative of the celebrity-obsessed press as a sparring contest: more surprising is that he sees the main adversary as himself. 'Richie's one of those blokes, like me, that when he does start talking to try to help you out, he'll condemn himself. He'd say to me, "Look I don't really want to be seen as a womaniser" - then in the next breath he'd tell me about the time he f***ed a stenographer in the court broom closet.'

Crowe's own hound-dog days are over since marrying old chum Danielle Spencer in 2003. Though his most significant long-term relationship is surely with director Ridley Scott, who he considers 'the governor, mate, y'know?'. Not only have the two made Gladiator (2000), A Good Year (2006) and now American Gangster together, they're currently shooting al-Qaeda thriller Body Of Lies and thrashing out the script for Nottingham, starring Crowe as the mean old Sheriff. 'We're going back to the original ballads, where Robin would chop off your head and hands, take all your money and not give anything to anybody.' No wonder he protects his small son with: 'Daddy makes DVDs but they're not good enough for Charlie to watch.'

Is it fatherhood that's mellowed this Aussie wildman? Even his relationship with Scott seems calmer. 'We're perfecting the art of the wordless argument,' laughs Crowe. 'We have differences of opinion but we don't clash. Look, I know some of you will assassinate me for saying this but what Ridley and I know about each other is that we get on because we're both very kind and generous people.'

Yet another seemingly straight-from-the-heart insight lanced through with seemingly waggish paranoia. Crowe's never exactly guarded, indeed 'interior monologue' is clearly a foreign language to him, but you can detect a new diplomacy, born of the fact that 'my bottom is covered in the bruises of my own comedy coming back to bite me'.

Quizzed about his Oscar hopes, Crowe groans: 'Aw come on, you can't engage in that kind of conversation without sounding like a complete f***ing w**ker.'

But beneath that blokeish exterior beats a luvvie's heart. 'This is probably gonna come across as archly pretentious but this gig is a calling, man. Especially when you have to put up with all the s*** that comes with the job? You've got to love it at its core.' He leans forward, beaming with Oscar-worthy honesty. 'And I dig it, man.'

I came ready to bury Crowe - but I can't help but praise him.

American Gangster is in cinemas from Friday.