Taking stock with one smoking Colin Farrell

He doesn't trade in hammy stock phrases (preferring instead to entertain with his excellent command of swear words), nor does he bother covering up the packet of cigarettes on his table to pretend he doesn't smoke. And there is no attempt to claim that his work hasn't brought him privileges.

"Someone once asked me, 'Is it hard for somebody to get sober in the public eye?'" he says, leaning back on the sofa.

"And I was like, 'God, I see what you mean, but f*ck no'. I mean, so many people come out of rehab and try to get their sh*t together, and they've lost their jobs and their families. I came out of rehab and I had two films lined up, a nice home and my kids were OK."

Sober and drug-free since leaving rehab in 2006, Farrell's career has also had a bit of a health-kick.

Gone are the action-packed blockbusters that made his name, the Daredevils, Phone Booths, the Miami Vices, and in their place are the art house, the offbeat and the downright dark, with In Bruges, Seven Psychopaths and True Detective providing recent substance.

But it's not down to some master plan. "I f it was planned, I would have been planning it for f*cking 15 years, you know what I mean?" he reasons, smiling. "Every single job I've done, I've gone in hoping I can make something that is in the least worthy of people giving and hour-and-a-half or two hours of their time, and 10-15 quid for the ticket."

And true to recent form, his role in his latest film, The Lobster, is an unexpected choice - and certainly worthy of a tenner. Directed by Yorgos Lanthimos, the dystopian indie sees the 39-year-old playing a pudgy, middle-aged divorcee who checks in to a hotel where guests have 45 days to partner up, or else risk being turned into an animal of their choosing.

Ten years ago, the idea of Farrell - who is trim from his regular yoga sessions and undeniably good-looking - playing chubby middle-aged singleton David would have seemed farcical. So what did Farrell make of the description?

"Ten years ago!" he scoffs, not missing a beat.

"I read a script I was offered recently that said I was 'early middle-age'. It was the first time I saw it in writing and I was like, 'F*ck, that's cold!'"

While he "f*cking ran" with the idea of eating his way to David's pot belly, it was the meaty script that initially turned him on.

"I've never enjoyed watching me-self in things, but this is so remarkable and so different," says Farrell, with a deliciously Irish twang. "Everything about it; the musical composition, the framing, the look of it, the sensibility of it, the story... I have a soft spot for it."

The film industry seems to have a soft spot for it too, with many critics predicting that The Lobster will sweep up a raft of awards.

But with his sons - 11-year-old James and five-year-old Henry - around, it doesn't seem likely that Farrell will forget his feet are made of clay.

"I did an animated film called Epic that my sons didn't go for, which was f*cking typical!" he says, laughing and shaking his head. "They were like, 'Can we put on Wreck-It Ralph again?' I went back down to earth..."

That their dad has a role in the much-anticipated screen version of J.K. Rowling's Fantastic Beasts And Where To Find Them impressed his sons - "for about seven seconds" - but Farrell is not smarting.

If anything, he's pleased his boys have very little awareness of his job, to the extent where he had to explain his work to his disinterested youngest son recently.

"Henry saw me on a poster one day for A New York's Winter Tale and said, 'Why are you kissing a girl?' I was like, 'Jesus, I've already missed it, I've already f*cked up. It's too late now, but anyway, let's get into it'.

"I was like, 'I'm an actor and do this and that and movies', but he's bored by it - he doesn't give a flip - as he should be. It holds none of the value that it does for us in our teens, 20s and 30s, when we become obsessed with fame as a vehicle for popularity and substance."

Family has always been a bedrock for Farrell. For all the past tittle-tattle about his love life, it's his mum, Rita, who often accompanies him to premieres, and it's his young family who are the centre of his world.

"The boys' lives are in America," says the actor, whose mother recently remarried and is also now living stateside.

"Their mums are there, so that's not even my call any more, which I'm fine with. Ireland will always be there and it'll always be home in many ways for me, but they're happy at school now and I'm happy over there."

Although he's not in a relationship at the moment, he's pragmatic on whether dating in the public eye is difficult.

"If you have a bit of celebrity and you want a casual thing, well then it's probably easier, but if you want a relationship, maybe people expect you to be a certain way and think a certain thing about you," he says. "But I think it's hard for everyone."

Though he jokes that he's sometimes the "odd bloke at the table" surrounded by couples, he can see the appeal of coupling up.

"We're all just trying to find our way through this panoply of human experience and it's tricky," he says.

"It's tricky to do alone and it's tricky to do with someone, but I do think that it's the ideal, not as a desperation or as a need, but the idea of sharing your life with somebody that you choose to share it with is the most beautiful thing imaginable," says Farrell.

"I know within that, it can get tricky, but it's the idea of consciously sharing your life with somebody and going through the hardships. I've never been able to get there, but I think it's a beautiful thing."

:: The Lobster is in cinemas now