Colin Mills, the managing director of Carat, is leaving the agency, ending months of speculation over his future.
Mills, 39, has been the managing director at the agency for six years, and joined Carat 11 years ago.
He leaves this Friday but handed his notice in several months ago. Neil Jones, Carat's commercial director, will replace Mills in the short term as the acting managing director.
Mills' departure follows a series of changes at Carat's parent company, Aegis, last year. These included the departure of the Aegis UK and Ireland chief executive, Mark Craze, who was replaced by Nigel Sharrocks, the Warner Brothers managing director.
Sharrocks said he and Mills had worked well together, but that Mills had decided he had spent long enough running Carat. He explained: "It takes it out of you, running a media company. I've talked to Colin about a job working alongside me in Aegis, so he may be coming back."
Mills said he will be taking a "short sabbatical" before considering his options. "I've been here a long time and I made my mind up a long time ago that it was time for a change, but due to various things that were going on, it wouldn't have been fair to leave until now."
Rumours that Mills had resigned were rife in the industry last autumn, but Mills and Sharrocks flatly denied he would be leaving the agency. Group e-mails were even circulated around Carat to reassure staff that Mills wasn't leaving.
The agency is thought to have been delaying news of his departure until two key pitches, Diageo and Unilever, had been concluded. Carat retained its Diageo account in the autumn, while Unilever's pan-European account went to MindShare in November.
Mills said he would consider the Aegis job offer as one of "several options".
Craze, his former boss, has been linked with a return to the industry to run the UK operations of KR Media, launched last year by the former Aegis directors Bruno Kemoun and Eryck Rebbouh.
The Aegis chief executive, Doug Flynn, is also reported to be considering joining the Australian publisher Fairfax.
- Perspective, p14.