Not for nothing is Coyne, 45, known as the most charming man in rock. Part evangelical preacher, part mad scientist, Coyne's boundless enthusiasm about art, life, everything, is contagious. His childlike wonder at the world is reflected by an endearingly upbeat vocabulary that makes liberal use of words such as "Gosh" and "Wow".

Coyne tells me about presenting a prize at the Brit Awards. You'd think he'd been offered a trip to the moon. "I'm always hearing these musicians being cynical about the Brits. Come on, live it up a little. I'm thinking, ?What, you're asking me would I like to go to party and have a good time and rub shoulders with Madonna and Paris Hilton? Of course I would. My wife, Michelle, came with me. We had a ball."

Since 1983, the Flaming Lips - the Oklahoma trio also comprising bassist Michael Ivins and multi-instrumentalist Steven Drozd - has been sustained by Coyne's febrile imagination and fanatical pursuit of new sounds and ideas. They have survived drug addiction (Drozd used heroin throughout the 1990s), endless line-up changes (Mercury Rev's Jonathan Donahue was once a member) and near penury to become one of the most critically feted rock bands of the era. Following their last millionselling album, Yoshimi Battles the Pink Robots, Chris Martin, Elijah Wood, Jack White and Justin Timberlake have all proclaimed themselves fans.

Now Coyne and co are about to release their 11th LP, At War with the Mystics. The album marks a shift in tone for the band famed for their cosmic lyrical sensibilities and oddball brand of psychedelic rock.

Where previous projects have seen them revelling in a fantasy world of Vaselinesmeared toast, all-conquering superheroes and flying asteroids, here their concerns are somewhat closer to home. For the first time, politics has crept into their lyrics.

"With what's going on in the world, and with Bush and his band of buffoons in charge of our country, you could say that we're working through some frustration and anger, " says Coyne with customary cheer.

"We're not saying, 'Let's all go kill George Bush, ' or anything. We would never make protest music, and I don't necessarily think that music can change the world. But the idea of ignoring Bush and this war is ridiculous too."

I note that, for all their escapist whimsy, the Flaming Lips' songs have always had a dark undertow. ?Do You Realise?', the Spectoresque single from their last album used for a series of Mitsibushi TV ads, came with a stark view of life and death: "Do you realise that you have the most beautiful face?

Do you realise that everyone you know some day will die?"

"Sure, " nods Coyne, "I think in our earlier stuff we sang about life being hard and unpredictable and we would always speak of this existential uncertainty and despair. But I don't think we really knew. As you get older you really do have true experiences with life and death. You don't look to the universe for any answers any more. The only answer is your own experience and the experiences of those around you."

Death has loomed large in Coyne's life in recent years. He lost his father to cancer in 1997 while his mother died in 2004 during the recording of the new album.

"The experience of losing someone changes you more than any book you could read or movie you could watch. But it's not a case of the grass was green and it's now grey. The sunsets are still beautiful.

"The day my mother died Michelle and I watched the sunset, not because it was poignant but because we looked over and it was there. It was hard but my mother's death didn't take everything good out of our lives. As these things happen I will stand up again and say the world is wonderful.

Just 10 years ago people could have looked at me and said, ?What do you know? You've got this great life, you're in a rock band and you can do what you want.' But now I can say ?Hey, I know stuff.' If anything, we've accepted that there's limits of optimism and that there's some value in hopelessness."

In professional terms the Flaming Lips have had hard times, too. The band spent their first decade trawling the US college circuit, playing to small and largely unmoved audiences. It wasn't until 1991 that they signed to a major label, though with their outlandish musical output they seemed destined to remain on the fringes of American alt rock. Aside from an unexpected US hit in 1993, ?She Don't Use Jelly', about a woman who breakfasts on Vaseline, they didn't trouble the charts.

But then came 1999's The Soft Bulletin, a spectacular album hailed as a modern psychedelic masterpiece that elevated the Flaming Lips from impoverished outsiders to financially viable indie heroes. Their follow-up, 2002's Yoshimi Battles The Pink Robots, was an even bigger hit and was hailed by some more excitable critics as comparable with Sgt Pepper and Pet Sounds.

Now, it seems, the Lips are on a roll.

Coyne is considered starry enough to appear at the Brits, while ?The Yeah Yeah Yeah Song', the first single to be taken from At War with the Mystics, is expected by the band's record company to sail into the top 10.

Yet Coyne insists there's been no masterplan to make them appeal to the masses. "In my mind we are still legitimately weird and I've never thought of our music as having any commercial potential, " he says.

The Lips' legendary live shows have also been crucial to their success. A firm believer in the value of entertainment, over the years Coyne has hatched a series of hare-brained plots to win over audiences. Performances have been known to take in glove puppets, animal costumes, buckets of fake blood, confetti, glitterballs, gongs and Coyne rolling across the crowd in a giant plastic space bubble. Not all the schemes have come off quite as planned, however. In 1997 he came up with the "Parking Lot Experiment", in which he wired up 50 car stereos in an underground car park in order to create a single piece of music. You had to admire his ambition, though the result was at best chaotic.

Coyne blithely admits that, as a result of his stage antics, most people tend to assume he's either crazy or on drugs. The band's former manager Michele Vlasimsky once remarked: "These are not normal guys from normal families - you're talking about freaks."

However, an hour spent in Coyne's company reveals him to be apparently sound of mind. And contrary to popular belief, he says he hasn't taken LSD since his teens. "I'm always having to convince people that I do normal stuff like washing dishes and cleaning the gutters, and I'm not permanently off my head. The desire to roll around in a space bubble is just one side of my personality. And wouldn't most people do it if they had the chance? The difference is that I really do have the chance. Ain't that great?"

For the endlessly energetic Coyne, the novelty of being in a successful band is showing no signs of wearing off.

"This has got to be the coolest job in the world. It's all about opportunities and what you do with them. I see other bands and they've got all this money and all this attention, they've got this audience waiting to love them and all they want to do is complain. The difference with us is that we can see how great it is."

The album 'At War with the Mystics' is out now. The Flaming Lips play with Bob Dylan in Kilkenny on 24 June