All pictures Alyson Blanchard/ShootsFamousPeople.com.

Looking back at the list of Mercury Prize winners since the award was inaugurated back in 1992, you could easily conclude that the judges have had a pretty good hit rate for spotting future popular classics. Winners include debuts from Suede, Dizzee Rascal, Franz Ferdinand, Arctic Monkeys and Klaxons, and breakthrough records from previously obscure acts including Pulp's Different Class and Elbow's Seldom Seen Kid. If there's one thing the list of winners mainly is, it's a roll-call of big mainstream successes (with some notable exceptions, of which more anon).

That's if you're not paying attention, of course.

Back in 2006, the Independent's Andy Gill postulated what he called The Curse Of The Mercury. Gill's view, broadly, was that the Mercury panel were so self-consciously concerned with appearing politically correct and cutting edge, that they were routinely awarding the prize to undeserving winners, damaging the prize's credibility, and turning it into a millstone around any future winner's neck.

The Mercury doesn't do much to challenge this narrative; it certainly likes to bask in its reputation for supposedly picking outside long-shots who later turn out to be the people's choice. "The music on the album is the only thing taken into account" sniffs the official website, and Gill's analysis overlaps enough with this; what Gill thinks of as bad calls, the Mercury can defend as heroically quality-based decisions, and hang the commercial results.

But there is, of course, another possible explanation. Perhaps the Mercury tends to back acts already locked into an irreversible rising wave. Certainly, Suede, Franz, Elbow, Arctic Monkeys, Pulp, Dizzee, and especially the prize's first ever winner, Primal Scream's Screamadelica were all unstoppable forces by the time the Mercury shone its spotlight in their direction.

When this tactic works, it makes what is a consistently conservative prize look like the more mature, intellectual, sophisticated alternative to the crass hullabaloo of the BRIT awards, celebrating a sort of smart eclecticism. In reality, the Mercury and the BRIT awards were both founded by the BPI (the UK record industry's trade association) and both serve precisely the same corporate interests, with the winners selected by closed panels of industry figures with the odd journalist thrown in to keep the press on side. It would be unfair to suggest that none of these people are sincere lovers of music, but it would equally be absurd to claim that industry interests do not influence the selection heavily.

There are some surface differences, of course. The BRITS doesn't even pretend to be focused on promoting artists; the BRITS are self-evidently awards for the best products produced by the British industry. The Mercury, on the other hand, goes to great pains to claim this is about nurturing acts, with both exposure and a 20 grand cash prize.

So what is the industry's interest here? Well, the Mercury Award is a single award, for the year's best LP. There aren't genre or gender categories, there aren't runners up, and there aren't any pop or singles-oriented acts in the running. What there is is an annual opportunity to whack a "Mercury Nominated" sticker on a dozen albums, giving each one a bit of a sales boost, and hopefully a lot of a sales boost to the winner. And it obviously benefits the industry most to whack those stickers on acts that are looking like they could be sellers, but need that little extra push. Seen through that lens, the absence of the likes of Oasis, The Prodigy and Blur from the winner's list (much puzzled over during their respective moments of glory) starts to make a lot of sense. Why bother wasting the sales booster on albums that are already doing fine? Especially given that you're going to garland those bands over at the BRIT awards anyway?

Occasionally, of course, this approach hits the buffers. Roni Size / Reprazent's New Forms (1997's winner) was already a critical smash and solid seller before the Mercury came knocking. That nobody predicted that this was a commercial peak for Size's increasingly abrasive and difficult music rather than a stepping stone to further success still doesn't make it the "outsider choice". Size was highly in demand as a DJ and Reprazent as a live act were already something of a fixture on the festival and legal rave circuit, and remain active over a decade later. It would seem that Size simply found mainstream acceptance uninteresting, and didn't pursue it further.

Of the award's other winners over the years, only 2002's Ms Dynamite and 1999's Talvin Singh really fit Gill's model, with music careers that stalled pretty much as soon as the Mercury glow faded. The other examples he cites — Badly Drawn Boy, PJ Harvey — have simply continued to follow the same wayward paths they were already on. It's absurd to suggest that an artist as smart and creatively restless as Harvey is trying and failing to be a mainstream pop star, rather than trying and succeeding at being something else.

Which brings us to Speech Debelle, 2009's winner and currently being talked up as precisely the kind of underdog victory the Mercury myth depends on.

Having sold a mere 7,000 copies and downloads of her debut LP Speech Therapy before the award, Debelle was widely seen as the token rap act on the shortlist and not much more. However, when you stop to think about it, Bat For Lashes, Florence and the Machine, Glasvegas, and La Roux all had little to gain in terms of increased profile, and Led Bib and Lisa Hannigan were even more token than Debelle (Jazz and Folk respectively).

So actually, this win makes a lot of good business sense. That's not to knock Debelle herself; Speech Therapy is a intelligent record, full of sharp lyrics engagingly delivered over living room-friendly jazzified pop (Jools Holland handing her the award was fantastically appropriate). It is at least Pretty Good and has flashes of being Bloody Brilliant. But equally notable is that out of every record on the shortlist, Debelle's is the one with the most potential for a significant change in its fortunes (The Invisible's debut and The Horrors' Primary Colours are already doing about as well as such deliberately challenging records ever will).

The Sunday night gig I attend at Manchester's tiny Night & Day cafe is an interesting one. Not quite full, but certainly fuller than it would have been pre-Mercury, there is a tangible sense of curiosity in the air. This is clearly not, in the main, an audience of people who are already fans of the album, but rather an audience ready to be won over, if Debelle can do it.

And by and large, she does. The most apparent thing is that Debelle already knows how to work a crowd, and given slightly larger crowds to work, will likely get a long way on sheer charm alone. Alternating between a sort of studied nonchalance and gobby older sister cheekiness, she pretty much has everyone in the palm of her hand throughout. The mere mention of a lack of wine on the tour-bus has one over-excited fan immediately fetch a bottle from the bar, which Debelle eyes with mock-suspicion: "I'm from South London; you need to confirm the safety of this".

As a rapper, she's certainly impressive. Debelle has cited Tupac Shakur as a significant youthful influence, and she possess something of his fluid polyrhythmic delivery. Debelle is very much a rap artist, rather than a hip-hop one, with rhyme schemes designed more for stream of consciousness musing than rhythmic force, and her complex and wordy lyrics could easily become unwieldy without such dexterous delivery. She has described her ambition to make to make "a hip hop version of Tracy Chapman", and there are definite echoes of the confessional singer-songwriter lineage of Chapman and her own muse Joan Armatrading in here.

The downside to this is the extent to which the actual music is merely a backdrop; often agreeably hummable, but rarely adventurous and occasionally terribly hackneyed. The bouncy Sesame Street-isms of most recent single 'Spinnin'' and the jagged structure of her Micachu collaboration 'Better Days' show genuinely great potential, but the crowd at Night & Day are — unsurprisingly for an audience taking in a set of largely unfamiliar material — keener on the more obvious call and response chorus of 'Go Then, Bye'. Unfortunately, for this writer at least, this is the weaker stuff; the song bears an uncanny resemblance to Estelle's breakthrough hit '1980', only with the lush Sugarhill Gang sample and infectious swagger replaced by borderline twee acoustic guitar and self-help book earnestness. "You're singing it like you want them to stay" jokes Debelle towards the end, but in truth, so is she; the sharp acidity of her lyric writing is somewhat undercut by the beatific mellowness of her band.

In the end, the Mercury win leaves Debelle at a curious point; as a stage performer, she is undoubtedly ready for a bigger audience, but the material itself may currently be too slight for the inevitable exposure to the wider pop audience the Mercury brings with it. That said, the collaborations with Micachu, Roots Manuva and the hard-as-diamonds Loose Cannons remix of her early single 'The Key' all suggest that Debelle has one eye on a more diverse future.