The Mercury Prize - A chorus of approval

It's a slippery beast, the Mercury Prize. When Antony and the Johnsons won in 2005, Antony Hegarty likened it to a "contest between an orange and a spaceship and a potted plant and a spoon" (come on, who wouldn't plump for the spaceship?).

Each year, the Mercury sets itself the task of first selecting the top 12 UK and Irish albums of a given 12-month period, then, a few weeks later, of picking the absolute best. Dusty jazz is judged against pin-sharp electronica, platinum-selling pop against obscure, woolly, folk, and nobody really knows exactly what the criteria are. Not even me, and I was a judge three years running.

I'm not sure how they selected me for the 10-person panel. I was on holiday in 2004 when a call came out of the blue asking if I fancied being a judge. It sounded like fun (and important fun), so I agreed. A week later, a courier arrived at my front door laden with boxes filled with CDs – hundreds and hundreds of them. Alas, there was no helpful checklist of points to look for: just the CDs and the expectation that I'd listen to each and every one of them. (Oh, and no, they don't pay you to be a judge.)

The criterion I tried to use was simple: I just rooted for the records I enjoyed listening to the most. Some of those were albums I'd loved for months, others were ones I hadn't heard until the boxes turned up. That said, picking an absolute favourite was definitely harder some years than others – Arctic Monkeys' Whatever People Say I Am, That's What I'm Not really had to win in 2006, but I still couldn't tell you which I love more out of A Grand Don't Come For Free by The Streets and Franz Ferdinand's self-titled debut. Luckily there were nine other judges on hand to tip it in Franz Ferdinand's favour. Of course, the simple show-of-hands voting system meant that my favourite album didn't always win, but the one supported by the most judges always did.

This year's list is one of the strongest in ages, which is why I don't envy the 10 judges who'll be settling into a plush ante-room in the Grosvenor House hotel next Tuesday afternoon. And they really will decide it on the night. Many people, the bookmakers included, seem to think the winner is all but confirmed long before the day of the ceremony. As a judge, it was always funny how the betting odds for the prize seemed to vary wildly throughout the period between the shortlist being unveiled and the winner being announced. You began to wonder if they were intercepting your emails or had gained access to the "most-played songs" list on your iTunes.

But the simple truth is that the winner won't be decided until it's narrowed down to two or three front-runners and a vote is taken, about 10 minutes before Jools Holland announces it. The bookies seem convinced that the name he'll read is Burial – the South Londoner's haunting dubstep electronica is 4-5 favourite – but who's to say that four or five of the judges who haven't yet fallen in love with Neon Neon's Eighties-tinged electro-pop (14-1), or Laura Marling's heart-stopping confessionals (8-1) won't force a victory for them?

It's well nigh impossible to predict who the judges will pick, with the absence on the shortlist this year of an über-hyped new band (à la Arctic Monkeys) just making the second-guessing harder. There hasn't even been a media-sponsored scene this year to help direct the judges towards a winner – only last year's judges know whether Klaxons would have still walked away with the prize if 2007 hadn't been the year nu-rave was foisted upon us, making them seem entirely "of the now" (even though the album wasn't all that good).

Still, there's no denying that the Mercury serves a important purpose in UK music. The prize was established to draw attention to a wide range of music that might not otherwise get it and to help record sales during the sluggish summer months. And, although there has been comparatively little sales-boosting this year (only one of the short-listed albums, The Last Shadow Puppets' Age of the Understatement is currently in the top 40 album chart, and even that's at No 40), it has no doubt raised the profiles of its nominated acts.

You might say, then, that it doesn't matter who wins; that it's the taking part that counts. But, to the judges, it matters a great deal. They want the prize to go to the most deserving act, for making the most deserving album. That way they might be deemed by hindsight to have got it right, something definitely not afforded to 1994's panel, who somehow picked M People's Elegant Slumming over Blur's Parklife. It seems that, that year, they really did prefer the spoon to the spaceship.

The winner of the 2008 Nationwide Mercury Prize will be announced on Tuesday