Phil Georgiadis is to leave Blue 449, the media agency that he co-founded, after 21 years.
He is stepping down after parent company Publicis Media decided Blue 449 should become part of sister global network Spark Foundry, except in three markets, the US, UK and France, where Blue 449 will continue to operate for local clients.
Georgiadis, the global chairman of Blue 449 and UK chairman of Publicis Media, has a reputation as one of the most entrepreneurial media agency leaders in UK advertising.
Industry chiefs paid tribute to Georgiadis as "one of the all-time greats of our industry" and "the most thoughtful media person I’ve ever worked with".
Georgiadis, who turns 57 later this year, will leave at the end of March when Publicis Media is set to complete the move of all its UK agencies to a new London headquarters in the revamped former BBC Television Centre in White City.
Simon Davis, the UK chief executive of Blue 449, will continue to head the agency and will also take responsibility for Spark Foundry in the UK.
Georgiadis said: "Now is the right time for me to move on. I have been fully involved and supportive of the new network strategy and I am obviously delighted that Blue 449 will retain its distinctive position in the UK market.
"This is testament to the whole team under the strong leadership of Simon and in truth they are doing a brilliant job without me.
"More recently I have enjoyed my role as chairman of Publicis Media UK. Having been heavily involved in the decision to move to Television Centre and in the fit-out itself, I can see it will be a catalyst for even more transformative behaviours and I wish Steve [King, the global chief executive], Sue [Frogley, the UK CEO] and everyone based there every success in the future."
King said: "I would like to thank Phil for everything he has done in leading Blue 449 and latterly in his role as chairman of Publicis Media UK.
"He is without question one of the all-time greats of our industry. His pioneering spirit and entrepreneurial drive is the very reason why he is so highly admired by clients, industry peers and colleagues alike."
Georgiadis set up Blue 449, then known as Walker Media, as an independent media planning and buying agency with Christine Walker in 1998.
Walker Media went on to win blue-chip clients including Marks & Spencer and Barclays.
Walker and Georgiadis each made millions of pounds as M&C Saatchi, originally a minority shareholder, upped its stake. Walker Media was valued at £48m when M&C Saatchi sold a majority stake to Publicis Groupe in 2013.
The media agency rebranded as Blue 449 in 2014 and doubled in size over the next five years as it won new clients, notably Asda.
Blue 449’s valuation rose to £100m when Publicis Media bought out M&C Saatchi’s remaining stake in February 2019 – a move that paved the way for Publicis Media to push through the merger with Spark Foundry.
Walker, who stepped down in 2007, described her former business partner as "very clever", "incredibly strong strategically", "very honest" and "very decent".
She and Georgiadis "never fell out in all those years" when they ran the media agency together.
"He was prepared to fight his corner for what he believed", she added, recounting how he once stood up to Marks & Spencer.
"M&S wanted to advertise in Vogue and he pointed out there was no M&S on Bond Street but there was a big M&S on Oxford Street," Walker said.
"Phil said, ‘M&S is a mass-market brand and you should be advertising in the Daily Mail.’"
David Kershaw, the chief executive of M&C Saatchi, said: "Phil, first with Christine and latterly Simon, built a superb business.
"He is the most thoughtful media person I’ve ever worked with. I’ve never been in a meeting with him where he hasn’t made me re-examine an issue."
Walker said Georgiadis has a serious, empirical side and is a fan of psychometric testing – so much so that he made them both do tests before they set up Walker Media and he would go on to test some senior employees on the same basis.
Georgiadis, who is affectionately nicknamed "Phil the Greek", also enjoys the fun side of the media business and has hosted a client day at the annual House Festival in London, ever since Soho House launched the event.
He spent the early part of his career at Benton & Bowles, WCRS and Initiative and has proved a shrewd investor.
Georgiadis was a minority shareholder in out-of-home media owner Outdoor Plus, which was bought by Global last year in a deal thought to value the business at close to £100m.