It marks the end of the brand’s 'Virtues' activity, which used four brand ambassadors - jiu-jitsu champion Roger Gracie, street dancer Zoe Green, BMXer Mark Webb and guitarist Steph Carter from the band Gallows.
Relentless is working on a number of special promotional projects to be run throughout 2012.
Professor Green’s appointment bolsters Coca-Cola's running commitment to music, which includes the brand's collaboration with DJ and producer Mark Ronson and singer Katy B for its global Olympics campaign and its new partnership with Spotify.
Professor Green has worked with brands Puma, Doritos, ZTE and Huawei. Coca-Cola described him as "perfectly blending credibility with commercial appeal".
A Coca-Cola spokesperson said: "It's the perfect ambassadorship. Both [Relentless and Professor Green] share a dedication to their art, both are defiant in the face of compromise, and both live life to the full in a truly no half-measures way."
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