Common’s Covent Garden suite is big enough to accommodate an elephant, but the one in the room is a metaphorical one. The previous night Common opened for his best friend Kanye West at the O Arena, West’s first show since his mother Donda died during cosmetic surgery. The headliner sang Hey Mama and promptly broke down at the end of the song. But Common’s camp say that the 35-year-old rapper will speak only on condition that no mention is made of West’s mother. Oh, and also anything else whatsoever to do with Kanye West.

It could be tricky. Even if Common doesn’t want to discuss his buddy’s woes, the two rappers pretty much come as a pair these days. How do you mention Common’s album Finding Foreverand its predecessor Be without mentioning the hip-hop star who produced them – not to mention the long friendship that precipitated them?

It’s a bit like being challenged to a staring contest by someone on the verge of sneezing. Less than a minute after hands are shaken, Common sips his soy chai latte and ponders West’s fame in a UK that has yet to embrace him in the same way. “Kanye has pop appeal over here,” he says, “whereas for me, it’s like rewinding ten years to when I started, trying to let people know who I am.”

In the States, though, there’s little to choose between the two. Indeed, a burgeoning acting career – including his part as a Mob enforcer in American Gangster – suggests that his profile as a media polymath is far from reaching its full potential.

It’s doubtful that the rapper – raised as Lonnie Rashid Lynn, Jr by his schoolteacher mother – would have dared confess to such lofty ambitions on his critical breakthrough album, Resurrection, in 1994. Styling himself as the antithesis of the West Coast gangsta scene, he recorded "I Used to Love H.E.R.," comparing the humiliation of a woman to the moral decline of hip-hop. He thought no one was paying close heed to the words, he says, and the way he talks about the ensuing uproar – incurring the wrath of Ice Cube on a 1995 song, 'Westside Slaughterhouse' – it isn’t hard to believe him. “It seemed unbelievable to me that he had even heard me. I grew up listening to Ice Cube, so for him to be paying attention to me was a joy in itself. Unfortunately, it was coming in the form of a diss.”

Wary of getting embroiled in hip-hop territorial warfare, Common did a very un-hip-hop thing: he capitulated. But pulling the offending song from his album wasn’t enough to prevent him from becoming a poster boy for rap fans who had become disillusioned with the increasing violence of the genre. “Backpack rappers” was the term coined for those whose worthy attempt to address the social problems of black America land them with a white audience.

Over the past decade, Common has become synonymous with the term. Speaking to The Times a couple of years ago, West suggested that being a “backpack rapper” was essentially a cop-out. “The average black person,” he sniffed, “doesn’t like underground hip-hop. That’s more of a white thing.” And yet Common was the wellspring of West’s early inspiration. Both from Chicago, the two first met in 1996 when West – described by Common as “this hungry, confident cat that would always want to battle with me on the mike” – was allowed to watch him at work.

You sense that had Kanye not steamrollered to the top of his profession at the first attempt with Late Registration, Common might never have dared to aim so high. Certainly, in 2002 when Common put out his fifth album, commercial success seemed the last thing on his mind. Electric Circus, one of the boldest departures of its era, unfolded over a frequently psychedelic backdrop.

There was Between Me and You, Liberation, in which the rapper reneged on homophobic sentiments he had expressed in 2000 on Like Water for Chocolate. “Growing up in Chicago in the black area, gay life was not prominent or respected, y’know? I’ve come from that, so I had to unlearn that and say: ‘Hey man, I’m not here to judge anybody’.”

In the years following Electric Circus, Common has entrusted his former protégé to repay the debt to his mentor. West is credited as the executive producer of both albums. Finding Forever was so titled, Common says, because he wanted to stake his claim in hip-hop’s pantheon of immortals. That might seem a little gauche were it not for the fact that it was this year’s most consummate hip-hop release. There were some unexpected cameos, too. such as Lily Allen on the recent single 'Drivin’ Me Wild'.

“Kanye said: ‘Do you know who would sound good on this? Lily Allen!’ I listened to her stuff and I was like: ‘Oh man, she would be fresh’. So we called her and she came to the studio after her show. She laid her vocals but at that point she was tired. So we had her come back and she was really fresh. We just vibed out, me and her. She kicked off her shoes and lit a cigarette and rocked it.”

In some ways, it’s surprising that West and Common should have got on so well. The champagne-loving West is garrulous, extrovert and combative. The wine-drinking Common is introverted and conciliatory – a Gordon Brown to Kanye’s Tony Blair; a Shrek to his Donkey. Inevitably though, if you spend enough time with someone, your traits begin to rub off on each other.

“Initially, my goal wasn’t to be at the top of the charts. But then Kanye brought together consciousness, saying: ‘Hey, I wanna be rich, I wanna be a superstar’.” He breaks off momentarily and laughs, as though surprised by what he’s just said.

The sticker on his current CD may display West’s name as prominently as his own, but, for the moment, their personalities are far from interchangeable.

— The album Finding Forever is out now on Island. Common supports Kanye West December 1 in Belfast; December 2, Manchester.