Former GroupM CEO Christian Juhl has been appointed to the board of directors of Martin Sorrel-led S4 Capital, the company confirmed on Thursday. He’ll serve as an independent, non-executive board member, S4 noted in a regulatory filing.   

The S4 appointment follows Juhl’s May appointment to the board of Boston-area based Akkio, an AI workflow platform designed for media agencies and marketers. 

Juhl was global CEO of GroupM (now WPP Media) from 2019 to September 2024 when he was succeeded by Brian Lesser. He then briefly served as president, corporate development until departing WPP in April of last year. Earlier he was global CEO of GroupM media agency Essence.  

Akkio, which launched in 2020 noted that Juhl’s appointment follows growing adoption by major media agencies including Horizon, Havas and LG Ad Solutions. CEO Jon Reilly said he brings a depth of knowledge and relationships to help Akkio build what he called "an operating system that works for the entire industry."