Founded by Jonathan Clark, Mark Buckingham and Janet McKay 12 years ago, the agency lost Buckingham to Grey after one year. Walpole replaced him at the creative helm and, in 2000, it was rebranded Clark McKay & Walpole.
But since it was bought by Media Square for £5 million in 2004, it has undergone a series of rapid managerial changes.
In March 2006, co-founder McKay left and was replaced by the managing director, Martin Nieri. Then, in October, the co-founder Clark announced that he was stepping down to take an advisory role.
Walpole left the agency on Monday and senior management are now searching for his replacement.
Nieri is supported by the creative director, Bob Nash, the planning director, Ben Rachael, and the client services director, Hamish Grant.