Williams will be responsible for the management and direction of all planning operations at the agency.
He will drive client development and the agency's overall business strategy as well as continuing to lead its award-winning Volvo business. Williams joined EHS in 2000 as a principle planner. He previously worked at Thorn EMI as a marketing manager.
Hamer said: "David's planning experience and client understanding makes him a great asset to the agency and the huge number of industry awards we have won for our Volvo work has been largely due to the fantastic standard of planning that he and his team provide. His presence on the board will be a welcome addition and I'm sure he will be instrumental in the continual growth of the agency."