To come clean at the start, I was never a fan of Madness in the old days, and I'm big enough to admit the fault was mine. I didn't get it, didn't get the humour, the wit, the melancholy, though it was all there. Maybe I just wasn't listening. Madness split up in 1986, many would say prematurely. When Divine Madness, their collection of singles, was released in 1992 and topped the charts, they reformed briefly to play a couple of gigs at Finsbury Park in London, and these were so rapturously received, Madstock became a regular feature.

Last year, on the back of an American ska revival, they were invited on a US stadium tour with bands such as No Doubt and the Mighty Bosstones. The fans turned out, word-perfect, to see the genre's granddads, the kings of vaudeville. Shortly after, what with one thing and another, all seven members officially regrouped, back with an album of humour, wit and melancholy and a skilled melodiousness that outdoes some of the best of their past. Which is fortunate for all of us and pretty OK for the band.

Madness come in two broad frames of mind; the optimists and the pessimists. Suggs, if he won't mind my saying, is a bit of a pessimist. I first met him two months back, when the band were invited to play "Our House" on The Letterman Show in New York. Madness are caperers with a Carry On sense of humour, but Suggs will always be a modern Tony Hancock ("I thought I got recognised in Camden the other day. Boy says to me: `Hey, mister.' I said: `Yeah?' He says: `Got any spliff?'"). The day after the show Suggs is hungover, but still looks so good, I tell him I'm jealous. "You shouldn't be, because I'm in pain and torture and wracked with paranoia. I feel sick. But I've learnt to accept that, y'know, a piano probably will fall on my head. Once you accept that, it's fine. What else can happen?"

But you enjoy performing? "I do enjoy it." Therapeutic? "Well, I get to a state of mind that maybe I can't in other situations. Pushing yourself right to the edge. I kept fucking up for 20 years because I was nervous... [Suggs does a good line in trembling hands] but now it's different - the difference between nervousness about your responsibility in terms of everyone else's welfare, which I had then, and being nervous because you should be, because otherwise you're not going to perform."

It's been said that Madness quit in exhaustion, toured to oblivion. "There was certainly a bit of that. Suddenly, you realise the wagon's out of control. You've forgotten who you are, what you're doing, why you're doing it. So we just stopped. Now people are doing it because they really want to." Suggs sips his hair of the dog. "And that has made it something really marvellously magical. The whole thing's been such an amazing revelation." He catches my eye. "Sorry."

Still, amid the jollity there remains an air of melancholy to the new songs, things that more than match "One Better Day". "Ten years ago, we'd been pushed around and called the Nutty Boys for so long that we started getting more and more serious as a sort of antidote. But that was equally false: it was the baby out with the bathwater. We've since discovered the best things are happy and sad at the same time. It's pathos, isn't it? But you see, you have to have some sort of education to know that. Someone has to tell you. Otherwise you go round in circles until you realise there's a word like pathos - it's all the things you're trying to get at, but you're just not sure where you're trying to get."

Forward to this week, where I'm speaking to drummer Danny "Woody" Woodgate and vocalist Carl "Chas Smash" Smyth who, on a sweltering day, is cucumber- cool in a cream duster coat. They are, they tell me, two of the band's biggest optimists. It doesn't stop them being honest. When Madness split, people took off on varied trajectories: bassist Mark Bedford studied typography and now has a design studio; keyboardist Mike Barson married and moved to Amsterdam. Woody didn't find things so easy. "I remember thinking, `What am I gonna do with my life?' Drumming was all I knew. I did think about getting involved in the record business in some way. But that's not me."

Smyth: "You could've worked in production. I always said that." Woodgate: "But I was lucky, I landed a cushy job with Voice of the Beehive. Except it wasn't cushy, because some of the time I wasn't getting paid." He chuckles awkwardly. So how were you managing? "Well, I didn't manage. My wife at the time had to go out and do courier work on a pushbike." He glances at his knees. Smyth reaches to grip his hand and Woodgate, not after sympathy, moves away. "It wasn't long really, just a couple of months. We were struggling a bit. And Voice of the Beehive came through in the end with the money. They were very good to me."

Chas, meanwhile, became an A&R man with Go! Discs, which showed him the music-business ropes from the other side of the ring. It's Smyth who was instrumental in getting the band back together, Smyth who came up with the album title Wonderful - and Smyth who wrote many of the singles, such as the troubling "Johnny the Horse".

"These two dossers used to sit at the end of my road drinking cheap booze, and one day one of them - Dempsey - was on his own, in tears. Turned out his mate had been kicked to death." Smyth's a big, bluff, sensitive bloke. He fixes you with a stare. "It's unbearable, isn't it? 'Course, if that's a single, no one will want a line like `Johnny the Horse was kicked to death'. Though Eminem can sing any sexist crap and get away with it."

Someone else with a big input was the saxophonist Lee Thompson. He wrote the new single, "Lovestruck", as well as "Elysium", which appears to be about manic depression. Smyth purses his lips. "I'm not being funny, but some of those lyrics disturb me."

"Lee's a great talent," chips in Woodgate. Smyth tries to continue. Woodgate has to raise his voice to be heard. "And an inspiration. Like, some of that early Madness wackiness - I couldn't cope with it. People like Lee helped me along the way. He was so outrageous, and he told me, you've got to let go. You've not got to care. Because people think about themselves. They're not worried about you, so even if you make a complete tit of yourself, they'll simply be entertained."

Smyth is composed. He didn't mind being shouted down. Though they're all fathers, Madness are a surrogate family among themselves - "we all had absentee parents, we're all potential loners". Smyth tells me lyrics are often personal - for example, Suggs's track "Saturday Night, Sunday Morning", a reassuring letter to his mates, some of whom felt trepidation on reforming. It goes: "I knew you'd come back/We always do/Like thieves returning/To the scene of the crime/But did they tell you everything has changed, just everything... And there was so much more I meant to say to you."

They're big men, Madness. I think we'll all be listening.

`Lovestruck' is released on 19 July; `Wonderful' in September (Virgin)