Harris co-founded the Aegis-owned digital agency Diffiniti with the current Carat managing director, Rob Horler, in 1996. The agency evolved from Carat Interactive. In his new role, Harris will work across the UM clients Microsoft, Xbox, MasterCard and Coca-Cola.
He replaces Rick Corteville, who has returned to his native US to take the role of global client director at the fellow Interpublic agency Reprise. Corteville joined UM from the Omnicom Group digital agency Organic in February 2008.
Jim Hytner, the president of UM EMEA, said: "We are really seeing some momentum with UM in the EMEA region and James will add to that momentum. We see the near future as ramping up the seniority of our staff and this is an opportunity to infuse digital even more into the agency."