And last month amidst slowing down of revenues and income and the growing clout of the FANGS - the board commenced an investigation charging Sorrell with personal misconduct and misuse of the company's assets.
Chairman Roberto Quarta will become executive chairman until a new chief executive is found, while Mark Read, a WPP digital executive, and Andrew Scott, chief operating officer, Europe, have been appointed as joint chief operating officers.
"WPP is investigating an allegation of financial impropriety by me, specifically as to the use of company funds", Mr Sorrell said in a statement. "It has been a passion, focus and source of energy for so long", stated Sorrell in an emotional note to WPP staff. However, I believe it is in the best interests of the business if I step down now.
Sorrell formed WPP from a shell company, Wire & Plastic Products PLC, establishing it as a marketing services group in 1986.
WPP said the probe had concluded, adding that "the allegation did not involve amounts that are material".
The 73-year-old Sorrell founded WPP 33 years ago, and grew it to more than 200,000 employees in more than 100 countries.
We pioneered Atticus Awards for original written thinking.... the WPP Fellowship Awards to recognize promising talent.... the Partnership and Practice Awards for client endorsed integrated market and case studies.
Sorrell is a titan of British business who was named the world's second-best performing CEO in 2017 by the Harvard Business Review. "And our highly talented people have always won through, always", said Sorrell. A new generation of management, led by Mark Read and Andrew Scott (who have each been at WPP for approximately 20 years), are well qualified and experienced in the Board's opinion, to deal with the geographic and technological opportunities and challenges our industry faces.
We welcomed J. Walter Thompson, Ogilvy, Young & Rubicam, Grey, 24/7 Real Media, Taylor Nelson Sofres, among so many others.
"In the coming period, I will be available to the Board and any of you, should you want help with anything, anywhere".
As some of you know, my family has expanded recently, WPP will always be my baby too.
With WPP operating in more than countries, Sir Martin has cultivated a global reputation as a commentator on economic and political matters, forging relationships with government ministers, financiers and corporate bosses around the world. "Good fortune and Godspeed to all of you ... now Back to the Future".
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Brooke Henderson takes Lotte Championship lead
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The IRFU have added that a review of the existing structures and educational programmes within the game will be carried out. It is therefore with great sadness and regret but with many cherished memories that I leave that behind.