Reid is promoted to the role from his position as group development director. He becomes chief executive in January but takes a role on the board forthwith.
Media Square has been hunting for a chief executive since June, amid reports that chairman Parry was in conflict with one of Media Square's largest shareholders, Peter Lynch. Parry argued that Lynch should not have a place on Media Square's board because he does not have appropriate experience. Last week another major Media Square investor was pushing for an EGM to vote on the issue of ousting Parry.
The company said today that Parry had always intended to appoint a chief executive during 2010, as part of a restructuring plan that started when he joined in July 2007.
Parry said: "The role of a combined executive chairman and chief executive is unsatisfactory from a corporate governance best practice but in 2007 Media Square was in such a deep crisis that the best way to manage a radical recovery plan was to create the role on a temporary basis.
"I am delighted that despite the ravages of the recession the turnaround has gone well and it is now possible to move to the far more conventional situation of a separate non-executive chairman and a chief executive."
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