Ed Meyer, the advertising patriarch who has ruled Grey for 36 years, is to retire, bringing to an end a career with the group that stretches back 50 years.
Grey sources said the terms of Meyer's exit had still to be finalised, but an announcement was expected to be made before Christmas.
Meyer, who will be 80 in January, controlled Grey with an iron authority until he sold the group, which he had a majority shareholding in, to Sir Martin Sorrell's WPP group in March 2005. He stayed on as the chairman and chief executive.
His years as the boss of Grey turned the one-time bed salesman into a very wealthy man. At the time of the takeover by WPP, Meyer was drawing a salary of $3.65 million and received around $500 million as a result of the deal.
Meyer also has a clause in his contract entitling him to office accommodation, support staff and expenses for five years after his retirement.
However, Meyer, whose appetite for work has always belied his years, plans to stay active and is understood to be setting up an investment company with his banker son.
Meyer described himself as Grey's "benign dictator", and he will be remembered for his autocratic management style.
He ran Grey as his personal fiefdom, rejected the idea of employee share options and attracted much criticism for surrounding himself with too many sycophants, failing to establish a clear succession plan and playing leadership candidates off against each other.
Steve Blamer, then head of Grey's North American operations, quit to join FCB, having grown tired of waiting to be named as Meyer's successor.
In August 2005, Meyer appointed Jim Heekin, the former Euro RSCG and McCann Erickson boss, as the chief executive of the Grey agency network, dashing the hopes of Carolyn Carter, the Grey EMEA chief executive, that the job would be hers.
- Comment, page 40
ED MEYER: TEN THINGS YOU NEED TO KNOW
1. For five years after his retirement, Meyer is entitled to office accommodation and support staff and various other expenses.
2. Much of Meyer's enormous wealth will be destined for good causes.
3. Meyer's advertising career started as a copywriter on Procter & Gamble's Lava soap.
4. He joined Grey in 1956. Fifty years on, Meyer was still working for the business.
5. Meyer is not the first to prove that running Grey is a passport to longevity. Arthur Fatt, the previous chief executive, joined Grey in 1921, and was still spotted there well into the 80s.
6. A legendary networker, it was said that it took Meyer 20 minutes to reach his regular table at New York's 21 Club.
7. On the lowest point in the WPP deal process: "The quality of food served at the law company. I'm not a sandwich man."
8. Meyer's opinion of retirement: "There are three reasons why I would leave. There is no more to be done, or the agency is not doing well and, since I'm the leader, I ought to take the fall. None of these have happened yet - but one of them will."
9. He is a frequent donor to the Democratic Party.
10. Meyer remains an avid reader and moviegoer, and was playing tennis well into his seventies.