The arrival of Greene King follows a review called at the end of 2003 when the brewer ended a five-year relationship with McCann-Erickson. Media remains with MediaCom.
MCBD saw off challenges from Publicis, Barrett Cernis and McCann to win Greene King, which is looking to build a distinctive personality for its flagship IPA brand. "It's been seen as a bit bland," one source said.
IPA, second behind Tetley in the UK cask ale market, will be relaunched later this year with a £2 million TV and press initiative aimed at increasing brand awareness and tapping into new markets. Greene King's portfolio also includes Abbot Ale and Wexford Irish Cream Ale.
The Met's assignment includes developing campaigns to support police operations against gun crime, domestic violence, street crime, burglary, drugs and terrorism, under the theme: "Working for a safer London."
Dick Fedorcio, the Met's director of public affairs, said MCBD was appointed "on the strength of its presentation, its impressive strategic thinking and its stimulating creative plans for the future".
Michael Pring, an MCBD board account director, said: "The nature of these campaigns means that getting the creative work right every time in terms of insight, approach and tone of voice is critical."