Goat has worked with clients including Dell, Beiersdorf, Meta, Tesco, Uber and Electronic Arts.
Mendelsohn and Justin Osofsky given additional remits as a result of the upcoming departure of business officer Marne Levine this summer.
Sorrell underwent surgery on Sunday (5 February).
Changes announced by Daryl Lee.
UK ad expenditure is forecast to hit £36.1bn in 2023.
Wacl has identified five areas for change in adland to help hit its target.
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