Pete Postlethwaite interview: For the love of Pete

IF YOU like your actors square-jawed, gym-honed and always sipping mineral water, you will be disappointed by the shambling and shilpit man who's somehow evaded the doorman at this swish hotel – but I don't and I'm not. Pete Postlethwaite isn't buffed, more scruffed. You could call his face lived-in, but squatted-in might be more accurate. And whatever he was drinking last night, it wasn't Highland Spring.

The last time we met, Postlethwaite treated me to the full guided tour of his amazing physiognomy, pointing out the dunts and gouges from playing rugby union in his youth, as well as those from rugby league, adding almost as an afterthought that his nose was broken three more times in pub brawls. I was worried there would be nothing else to say about his coupon today, but good old Pete, he's only gone and got himself a madman's beard. And what's that plum-sized swelling on his left cheek?

"My face blew up this morning," he says. "The doc's calling it a hypoenergetic reaction and he's given me a cortisone injection – in the bum." The swelling has affected his speech but, trouper that he is, a Shakespearean flourish is effortlessly mustered. "I think this bloody play is cursed. It's an embossed carbuncle in my corrupted blood!"

The bloody play is King Lear, which 63-year-old Postlethwaite has performed in Liverpool to disappointing reviews, but much better ones have greeted it in London. "It started off as this frenetic fireball, everything was thrown at it," he says. "But the actors ended up swamped by the mise-en-scene.

"So we simplified it. Three tables – the most expensive prop – were replaced by three envelopes. It's running smoothly now. Well, as smoothly as a rollercoaster. Imagine Nemesis at Alton Towers without a seatbelt – that's Lear. I tell you, it's cursed…" So let's talk about something else. I know, let's talk about the end of the world.

The Age Of Stupid is Postlethwaite's new film and here he could hardly complain of struggling to have his voice heard. He plays the last man alive, the curator of a museum 500 miles north of Norway, in what used to be snowy wastes. The film opens with London under water, Las Vegas under sand, and – most chillingly, given the recent fires which ravaged Australia – Sydney Opera House engulfed in flames. The year is 2055 and climate change has wiped out all but this archive eyrie where Postlethwaite's character bicycles among pickled animals stacked up two by two and copies of every book ever written, Jeffrey Archer included presumably – and flicks through old telly news footage in an attempt to discover how we managed to cock up so apocalyptically.

Postlethwaite has been Oscar-nominated (for In The Name Of The Father). He's starred in a thriller so thrilling it still induces a shudder at the mere mention of its title (The Usual Suspects). And for Jurassic Park – The Lost World he's had Steven Spielberg bestow on him high praise – "Pete's probably the finest actor in the world today" – and location trailers twice as big as this lounge. The Age Of Stupid may be big in scope but it's so low-budget that Postlethwaite didn't even expect to appear on screen.

"I turned up thinking I was just doing a voiceover and the producer (John Battsek, One Day In September] said: 'We've found you some money for a small caravan.' The film isn't about me, it's about one of the greatest challenges we face. Even so, and even though I was working for a vibrant young team led by a fine director (Franny Armstrong, McLibel], I thought I'd do my two days and the movie would be one of those which would just disappear into the ether. But, golly, the buzz has been fantastic. The film's gone berserk.

"Barack Obama's people have been in touch and he wants to show it – to the Senate, I think – so we're off to Washington next month. And Prince Charles has asked for a private screening at Clarence House." Postlethwaite says the film offers no solutions, but there are plenty of talking heads espousing sharp theories about wars for oil, the shopping religion, green energy and the wastefulness of a cheapo China-made plastic toys' circumnavigation of the globe, ending back in a landfill site in its country of origin. "If we can provoke some discussion on the issue, that would be a fine thing," he adds.

"The big subjects fall off the agenda so easily. They get debated for a while, but then people tire of them. The last time I was up your way was to speak at the Make Poverty History rally in Edinburgh. It was the time of the G8 summit so the campaign was massive. Where's Make Poverty History now?

"But since the economic crisis, where people who were always suspicious of politicians have stopped trusting the institutions as well, I think there's been greater awareness about the state of the planet. Maybe it's taken the plight of the polar bears – never mind what's happening in Darfur or Angola or Sudan – to bring that about. So be it."

Postlethwaite, though, didn't just become green the moment the stock market screens turned red: he lives in Shropshire in an eco-house complete with wind turbine, solar panelling and a woodchip stove. "I must give my wife Jacqui credit here – she educated me," he says. "She's very passionate about the environment, studied it for her OU degree and instituted the system where our rubbish gets recycled via 14 different-coloured bins. I'm joking. It's only 12…"

Born in Warrington, Cheshire, the son of a barrel-maker, Postlethwaite toyed with becoming a priest before being converted to acting, and he joined Liverpool's famous Everyman Theatre when it was committed to political work and the young turks included Anthony Sher, Jonathan Pryce and Julie Walters, with whom he had a romance.

He's made lots of films – "80 or 90, so I'm told" – and while Romeo + Juliet and Brassed Off were other successes for him, there were two he wishes he could erase from his CV. "One was called Beast, shot in Warsaw, set in an orphanage, the director was a fascist who was horrible to the kids. And the other was… do you know, I've clean forgotten."

There were a couple that got away. "I turned down Gangs Of New York because they wanted me to work for less than the union rate. When I asked why, the lawyers said: 'Because it's Marty (Scorsese].' Did Dan (Day-Lewis] and Leo (DiCaprio] agree to that? I rather doubt it." Legend has it he said "no" to $20m for Gone In 60 Seconds. "To me, that film said nothing about life. It's not that there can't be fantasy – I've done James And The Giant Peach and The Lost World – but in the latter my character says at the end: 'No more killing.' There was redemption. The money talked about wasn't 20 million but it was still obscene. You could have bought a lot of The Age Of Stupids with it."

Postlethwaite has two children, and the eldest, Will, is following in his footsteps. "He's in his first year at drama school and he's loving it. I can't see anything of me in him, Will's unique. Maybe his sister Lil is a bit like me, though at 13 she's sharper than I ever was." The father's advice was "Go for it, laddie", though bearing in mind the theme of The Age Of Stupid and also that of King Lear, he was wary about sounding like he knew it all.

"Because I'm playing Lear I've been asked a couple of times if I think the older generation these days lacks respect. I think it does, and I say: 'Bloody good thing'. Elders should no longer be seen as betters. They've started wars that were wrong and caused financial ruin and they're making a right old mess of the planet.

"We've got to hope the next generation will do things differently. I'm sure that in 20 years' time the kids will say: 'Can you believe that people actually used to smoke – put these funny little things in their mouths, lit them and sucked all that crap into their lungs?'" His voice now back to normal, Postlethwaite cackles the way only committed smokers can. And with another ride looming on the Lear rollercoaster, up and over that embossed carbuncle, he needs another fag. v

• The Age of Stupid is released March 20; King Lear runs at the Young Vic until March 28 www.ageofstupid.net, www.youngvic.org