Matthew Hook, chief strategy officer at Dentsu Aegis Network UK and Ireland, is leaving the business.
He joined Dentsu Aegis in 2002 and has held various positions over the past 17 years, including chief strategy officer and managing director at Carat UK and head of strategy and managing partner at Vizeum UK.
Hook is taking time out before considering his next move. Dentsu Aegis confirmed there are no plans to replace him.
Euan Jarvie, chief executive of Dentsu Aegis Network UK and Ireland, said: "Matthew has made an invaluable contribution to our network since joining in 2002, which we are most thankful for.
"During that time, he has helped shape and grow our business in the UK and the US, specifically made strong contributions to Carat and Vizeum, and played a key role in our network’s overall strategy and growth, as well as that of many of our clients. We wish him the very best for the next stage of his career."
Dentsu Aegis has had several changes at the top. Jo Sutherland replaced Rick Hirst as chief executive of Carat in April last year, while James Connelly, who founded Fetch, left in March this year. Former chief executive Stef Calcraft departed in December 2018 after less than a year at the company.
Hook added: "Over the years, I’ve been able to work with some extraordinary people, puzzle through some fascinating challenges and learn a massively wide range of skills. I’ll be leaving with many happy memories and the confidence that the business will go from strength to strength. For me, it’s the right time to try something new."