In their new roles Bowden and Dormieux will jointly run the agency, which has clients including EE, Morrisons and Lloyds Bank. They will report to Tom George, the chairman of MEC UK and Northern Europe.
Bowden has been managing director of MEC since June 2011, when he joined from Vizeum where he had been the deputy managing director for a year. He was previously the head of planning at MEC for three years between 2007 and 2010.
Dormieux was promoted to chief operating officer following five years as the managing director of the agency’s digital arm MEC Interaction, at the same time as Bowden’s appointment as MD.
George said: "We want MEC to continue to grow and be the most successful agency here. We were named agency of the decade last year [at Media 360] and our ambition is to be named agency of the next decade too.
"One of our great strengths has been the stability of the management team and it has always been our desire to maintain continuity and promote where possible from within.
"Our business continues to get more and more complex and that’s both exciting and challenging. The scope of delivering excellence to our clients, diversifying our business and winning new business makes it more demanding every day and we need an agile management structure to reflect this new reality.
"Stuart and Jason have been instrumental in the continued success of MEC and have very complementary skills in the areas that we believe are going to be critical in taking MEC to the next level."
As part of the changes, Sarah Hennessy, the deputy managing director, has been promoted to managing director and Paul Hutchison, the head of comms planning, has become the agency’s deputy managing director.
George said: "Sarah has done a great job as one of the senior management team alongside Steve, Stuart and Jason and her promotion is in recognition of this.
"In Paul we have a consummate client leader and his promotion recognises the importance of delivering a first class service to all of our clients."
Hatch is leaving MEC in April to become Facebook’s regional director for the UK and Ireland.