He became chief executive of Aegis Group in 2010 and of the wider Dentsu Aegis Network in 2012, following the acquisition of Aegis by Japanese advertising giant Dentsu. Tim Andree, executive chairman of Dentsu Aegis Network, will take on Buhlmann's duties by adding the title of chief executive. Buhlmann, who turns 59 this month, steps down on 31 December and will become a special adviser to Dentsu.