Found this randomnly on the BBC site. An old classmate of Gem gives an insight to him:

"Looking back he could always play. But somehow, Colin Murray Archer, rhythm guitarist with Oasis, never seemed cut out for greatness.

Don’t get me wrong, as he sat behind me in class at school, he had all the markings of talent, but as an artist rather than a musician. We nicknamed him Gem (with a hard g as in gifted.) A childish pseudonym of footballer Archie Gemmill, though we never believed him capable of such heights!

Though Gem’s lyrics were strong enough, sadly his voice wasn’t, and so once at Durham New College he recruited a lead singer in the scream of Simon Scott, an eclectic performer a la mode of New York Dolls. Had anyone made it big back then, truly my bets would have been on Simon.

After leaving their graphic design course, the boys bummed off to Newcastle, regaling the local pubs and clubs there with their renegade tinny sound.

Next I heard of Gem, he was giving it large as a doorman at a venue in London, the Bull and Gate, taking to the stage as I recall in the form of The Contenders. He faded largely from the Northern consciousness, until out of the blue in November 1999, a press release announced he was the new addition to Oasis, replacing a disillusioned Paul ‘Bonehead’ Arthurs.
My immediate circle was stunned. The local chatter was of how miraculously our classmate, who had sat shoulder to small town shoulder with us, had suddenly been relieved of at least five years of his actual age! Later the Oasis media machine changed his date of birth to match that of Noel.

Now father of two to Libby and Joel, it remained to be seen if Gem’s finger fluctuations could endear him to an Oasis ear, eager for earlier glories.

An Oasis live appearance had much eluded me until recently, when camera in hand, I grabbed the chance to check out their more mature manifestations.

The Arena in Newcastle, impressive in its impersonality, sweated to the beat of an early summer heat. Mr Cool Liam Gallagher, insisted upon keeping his jacket on at all times as a plethora of people swooned, quite literally before him.

I had expected a plucky plugging of the new album, but was pleasantly swayed by the sometimes languid lyrics of the gutsy guitars to the old tunes, our good times. Our rock and roll stars drank their champagne supernovas with ease and aplomb.

From the sidelines I watched Gem. His features much the same as I remembered, his grace with a guitar an easy alliance with Noel.

I tried to muster the memories of old, but sadly for me, in all their new democratic form, Oasis can never hit the heights of the first three albums. Can the wonder of Wonderwall ever be climbed over?

I would guess Gem’s best lyrical contribution to Oasis to date would stand as ‘A Bell Will Ring’, but personally I am much more impressed by his outstanding, and more personal, past performance with his boyhood Buddha Paul Weller.

Gem is a man of many talents and facets. He has his roots in the North, but is very firmly fumbling to find his feet out of it. Oasis seem ever determined to be remembered as a Liam and Noel duo, but their success has been scaffolded by a succession of shadow musicians such as Gem, whose talent often outshines that of the fame-hungry front men.

A distinct dislike of interviews, and with not a backward nod to his northern contemporaries, Oasis may seem reluctant to look back in anger, while Gem, now a rock n roll star, seems reluctant to look back at all....."

Here's a link to the article, worth a look for the two pictures of him really. To put it blunt, a huge contrast to the Gem we know now .