Clarkson joins joint managing directors Tim Irwin and James Jennings, board director Nick Kelvin, and broadcast director Andy Benningfield, on the management board.
The agency has also made two new hires, appointing David Fineman as head of digital and Mark Robinson as marketing director.
Fineman joins from Carat Digital, where he was account director. Robinson had been working with BJK&E in a consultancy role and prior to that worked at Aegis-owned media company Vizeum.
Tim Irwin, managing director at BJK&E, said: "We have now got a strong team in place which puts us in good shape for the year ahead. Katy has been a great asset over recent years and a driving force behind the outstanding work for Mercedes Benz. In Mark and David we are adding to our capabilities in new and exciting areas."
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