The Mercury Music Prize is a strange beast. It’s somehow come to be seen as an impressively credible music award, a gong which recognises artistry and creative achievement rather than record sales. This despite past recipients including hopeless yuppie pop disgraces M People and the faintly ridiculous Gomez. This despite the winner being chosen by an arbitrarily assembled collection of industry types who reach a decision via a process which makes FIFA’s World Cup bidding process seem almost transparent and fair. And this despite the shortlist consistently excluding any British musician who makes interesting, forward thinking music in favour of eight middle-of-the-road indie bands, two worthy but dull folk musicians, a jazz combo with no chance of winning, and Dizzee Rascal.

In 2008, that jazz combo was the Portico Quartet. Their album, Knee-Deep In The North Sea, inevitably lost out to Elbow’s The Seldom Seen Kid, but the nomination gained them a lot of publicity and won them thousands of new fans. It makes commercial sense for their record label to release a deluxe edition of Knee Deep: it’s the album that made them (relatively) famous, and its status as a Mercury nominee should, however inexplicably, ensure the odd impulse purchase. It makes artistic sense too, just about: this edition has been worked over by producer John Leckie, who the band worked with on the follow-up to Knee-Deep, Isla. As a result, the band would presumably consider it the definitive version.

Unless you’re a committed audiophile or a obsessive fan of the group, Leckie’s subtle, scarcely noticeable reworking shouldn’t tempt you into purchasing the album for a second time. Neither should the addition of three confident but unadventurous live renditions of album tracks. First time listeners will, however, find things to enjoy. The quartet make well crafted and understated jazz music, infused with elements of contemporary classical, and performed on saxophone, drums, double bass, and hang. The hang is a tuned percussion instrument which sounds a little like a steel drum: as a result, it lends the record an oddly Caribbean feel, even though the music – carefully written and performed, dense, unassuming, and never spontaneous – could otherwise not be less like the sounds associated with that region.

Their appealingly odd use of the hang is not the band’s only strength. Their songs are clever without being fussy, and are consistently embellished by neat touches, like the perky, poppy sax which enlivens ‘Steps In The Wrong Direction’. At its best, as on the wistful and pretty title track, their music has much to recommend it. At other times however, it’s pleasant to a fault; undemanding and often a little too sedate, it resembles the sound of waves gently lapping at your coffee table. At those moments, it’s difficult not to wish that the band would let themselves go a little more, abandon their carefully plotted course, and allow a little more life and spontaneity into their songs, perhaps via the improvised soloing with which jazz was once synonymous. A reasonably impressive record written by talented composers and performers, but a little too inoffensive and staid, Knee Deep In The North Sea is in many ways the archetypal Mercury-nominated album.