McKay's co-founder, chairman Jonathan Clark, saluted her contribution over the years since they established the agency in 1995, saying: "Janet has devoted a huge amount of energy and passion to make the agency the success that it is. Her humour, dedication and ability to motivate people will be sorely missed."
McKay is formally set to depart in March, four months after the agency signalled Nieri's status as her likely successor by giving him the new role of deputy managing director.
Nieri's background is in account management and, as client services director, he was instrumental in winning Peugeot from EHS Brann in December. He began his career at McCann Erickson Manchester in 1994, then spend six years at WWAV Rapp Collins before joining CMW.
Clark said: "We are extremely fortunate to have someone of Martin's stature and calibre to step into Janet's shoes."
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