Dave Gahan, the frontman of Depeche Mode, walks into a hotel suite in London in a three-piece suit with his hair slicked back. He looks dapper, fit and in good health, a veneer that doesn't sit with the exhausting fact that this is the final day of months of interviews around the world. It doesn't sit either with a hard-rocking career freckled with drug overdoses and a suicide attempt, and endless touring and scraps and serious cocaine and heroin use. In fact, he looks awesome, more Malibu than Priory.

The Sunday Tribune is here for a round-table interview with four journalists from Eastern Europe, posing a language barrier which vexes Gahan increasingly as the time passes. You can't blame his occasionally rising narkiness, as he has to put up with one possibly inebriated hack from the Czech Republic who keeps posing factually inaccurate questions about Anton Corbijn; a softly-spoken female journalist who speaks exclusively in gigantically incomprehensible philosophical terms; and a couple of German-speaking fan boys who insist on making him sign endless CD sleeves before and after the interview.

Anyway, in he strolls humming U2's 'Get On Your Boots'. Does he like the new album, I ask? "I was just listening to it this morning, actually. There are some really good songs on there. I think it's going to grow on me. It's not immediate. When I first heard the single, I was completely baffled, to be honest – it's like lots of different songs all put together. But I get it in the album, I understand it." Better still, he likes the accompanying film, Linear, that Anton Corbijn has made for No Line On The Horizon.

Comparisons with U2 often follow Depeche Mode around, which Gahan isn't really into. "I think that's probably the Anton [Corbijn] connection." Corbijn is a friend of the band and has photographed them extensively, as well as making their 1989 music video 'Personal Jesus'. Gahan pauses, "...and it just so happens that quite often we [U2 and Depeche Mode] put out albums at the same time," he cackles, a little manically, perhaps subconsciously realising the unfortunate PR setting this must pose.

Last time they played the same venue, "Bono sent over a note saying hello and being generally polite, I sent one back saying 'and you are?'" he laughs at the memory. One of U2's security team, Gerry, worked for Gahan years ago. "He took care of me – literally – for the 'Songs of Faith and Devotion' tour. He went through a lot with me. He's a great guy. He looks after Bono now." (he pronounces Bono, 'Bow-No'.) "Us and U2, we're similar in age and number of albums. We've both a big body of work. But there's a lot of life left in us old geezers yet."

As Gahan was working on tracks for Depeche Mode's new album Sounds Of The Universe, some of his demos somehow made it online. It infuriated him. In an era where music is constantly uploaded, duplicated, shared, nicked, and leaked, the reality of private work becoming public makes him very, very prickly. "There's an element of mystery taken out of the process. I find it kind of ridiculous. At the same time, it shows a keenness and an excitement, wanting to hear what's new. But there's nothing more insulting than having something leaked by a journalist before you've even had a chance to finish your own work."

Yikes! Is that what happened in this case? "I've no idea. It could have been another of those things." Oh. "It could have been a CD lying around somewhere that someone picked up. It could have been lost in translation over the internet when we were passing things back and forth to each other. It could have happened when I was laying down guide vocals in New York. When it's a finished piece of work like the Yeah Yeah Yeahs thing [referring to that band being forced to push forward their release date when their full album was leaked online], that's just wrong. I'm sure they're really pissed off about that... It's like someone painting a painting and saying, 'I did the charcoal part, I haven't finished yet, but what do you think?' It's crazy to me that people started making these ridiculous assumptions." Oddly enough, some of these demos will now find their way onto a box set the band is releasing on the back of the new album.

Gahan speaks about music pleasantly, if in lofty terms ("music changes the world for me, it changes my outlook on life.") We get an insight into the importance of Depeche Mode throughout Europe when the Czech journalist asks about seeing him playing in his home country in the Communist era in 1988. "For us, it was always about going somewhere we hadn't been before, and trying to perform in places where we knew that we had fans," says Gahan. "Poland, East Germany – we went to those places in the same way we would go anywhere else, same as Russia. What we didn't like was a lot of people got tickets through the police and through the government.

"When we first went to some of those places, there would be a row of police, then there would be a row of very special people, and then the fans. We tried to change that when we visited again. I remember the first time we played in Warsaw there being thousands of people on the streets when we played the concert, and then when we came out, there was not a soul anywhere. The streets had been cleared within half an hour. It was eerie, weird. We were marched back to the hotel and weren't allowed out. There was a curfew. It was pretty wild to people who hadn't grown up with those kinds of restrictions."

After a while, Gahan starts taking the piss out of questions. When the soft-spoken female journalist asks him what's next after "playing with angels and showing people what the universe tastes like", he jokes and half-sneers, "who knows? Maybe we'll do the first gig on the moon. Get Richard Branson involved or something."

Soon after this, with the PR lady who had been sitting dormant in the corner suddenly becoming animated as our time runs out, Gahan exchanges pleasantries with the Sunday Tribune, having thankfully not having not annoyed him throughout the interview. He rolls his eyes at the prospect of having to sign another bunch of CDs for the rest in the room. Nonetheless, he does it with good grace.