Roni Size is the man who has taken jungle to the next level. If Goldie's Timeless album was the catalyst for jungle's arrival in the mainstream, Size and his Reprazent collective have consolidated the former sound of the underground as an articulate and internationally acceptable musical language.

To hear just what Reprazent have done, take a listen to New Forms, their ambitious debut double album from earlier this year. Expansive breakbeats, neo-classical arrangements, primed roughneck rhythms, wonderfully ethereal vocals and the oddball chat of an MC created some beautifully sculpted tracks.

Rather than treating jungle as an extension of jazz as many drum and bass acts are prone to do, Roni Size and friends simply concentrated on extending and exploring the dynamics of the beat. Going buckwild with the breakbeat has rarely sounded quite so daring.

Such audacity has brought its rewards. Cited by many critics as one of the albums of the year, and spawning a couple of Top 20 hits since release, Reprazent's capture of the Mercury Music Prize in September was particularly noteworthy. Of course, the Mercury judges have made some unexpected decisions in the past (think M-People's success a few years ago) but few anticipated that an album like New Forms could triumph over such sleek marketing as Radiohead or Oasis. Nevertheless, the award and £20,000 cheque went back to Bristol. No one's sure where the actual award is these days - but the cheque was donated to a local community project.

Roni Size sees the Mercury Prize as a step in the right direction. "Of course I'm glad we won, you know what I mean. It's great and it's great for our music and for people who are doing what we are doing. What we're doing is brand new for some people. It's like when people saw us playing at the Mercury Awards - the people who saw us at that had probably never seen or heard drum & bass before, so we get a whole new audience from that.

"We just want people to listen to us with open ears. We didn't make this album for the money; we did it for ideas and experience. Anything else was a bonus. But we're only beginning. These are early days; anything still can happen."

New Forms is a pay-off for years of toil. While the likes of Massive Attack and Portishead propagated that certain Bristol sound - slow-motion hip-hop with a touch of the blues - Size was making abrasive metallic records for his own Full Cycle label and DJ-ing whenever and wherever there was a demand for his technic touch. His first Irish performance came during this period, playing to just 40 people at the Quadraphonic club in May 1996.

It took six years to progress from cutting his first rough dubplate to producing an album capable of captivating an international audience. "There were some tough times, yeah, but I knew what I was doing (laughs). Well, I knew where we were heading. It really clicked when the others arrived. We come from the same parties, festivals, carnivals, not together but at the same time. We bring different things to the camp."

Reprazent are a collective in the old-fashioned sense of the word; and while Size may be the centre of attention as far as most are concerned, the other members have played their parts in the New Forms saga. They have also been major players in the various Bristol scenes over the past 10 years. DJ Krust and Suv had a Top 10 hit as members of the Fresh Four with a version of Wishing On A Star a couple of years previously, while Die was in an early version of Bristol's house superstars Way Out West with Nick Warren. Add MC Dynamite and vocalist Onallee to the mix, and you have what their record label quite rightly refer to as "a breakbeat supergroup".

They are perhaps at their most spectacular when they play live, an aspect Size is keen to emphasise. "We're not just about releasing records - we want to do it live and prove that we can do it live. Some of the shows we've done have been dodgy but some, like one in Sweden a few months back, or some of the shows with Primal Scream, have been a dream. When we play live, we have a studio up there onstage, man, and things happen. We've gone and played the album live and now I'd love to go back in the studio and do it all over again."

While most dance acts are still shy when it comes to producing an attractive live show, Reprazent have proven to be masters when it comes to stagecraft. MC Dynamite prowls the stage and supplies superior lyrical flows, Onallee comes on like a latter-day Billie Holiday, the other four crouch over keyboards and consoles, occasionally remembering to jog on the spot, and a bass player and drummer add to the spectacle and the sound. It is quite a sight. No wonder Size admits that he wouldn't mind spending the next year on the road.

But New Forms was not an album born of jamming and freestyling in a rehearsal room. "I get a lot of my ideas from remixes I do from other people or when I'm DJ-ing," admits Size. Remixes also spread the drum & bass message to musical communities which have previously preferred not to listen. The Reprazent remix of Nu-Yorican Soul's It's Alright I Feel It, for example, is one of the year's finest, putting a junglist spin on Masters At Work's gorgeous house sheen. Size is fully aware of just what is happening within the various scenes: "It's gonna develop, just you watch. People are going to click on to drum & bass and accept it. This ain't no fashion thing."

It remains to be seen, however, just how fashion will take to New Forms. Just like Portishead's Dummy and Bjork's Debut before it, New Forms has the potential to become the soundtrack to smart dinner-parties and stylish hair salons before too long. The current marketing campaign for the album certainly seems to believe that such a scenario is inevitable. And it hasn't gone unnoticed that Size has a striking visual image that most jungle acts would give their collection of Metalheadz dubplates to possess.

But beyond the image, there remains the music. With cuts like Share The Fall, Brown Paper Bag and Heroes popping to the surface from New Forms, Reprazent have a unique grasp on the futuristic structures of their genre. Yes, there are occasional nods to jazz and to the other strains of black music which have contributed to the drum & bass make-up - but New Forms is more about new music than any other album released in 1997. Size agrees. "This is brand new music. But we haven't even started yet as far as I'm concerned. This is only the beginning. Just watch."

New Forms is now available on Talkin' Loud.