Ad marks third in series by features director John Madden.
Guardian ad chief has penned open letter to clients and agencies explaining rationale.
Group is forecasting 1-2% organic growth over course of 2024.
Annual report also reveals WPP chair Roberto Quarta will stay on longer than expected.
Alternative text helps people with sight loss gain a mental impression of a visual.
North America saw revenues fall by 2.7% for the year, while APAC, Latin America, Africa, Middle East and Central and Eastern Europe grew organic revenues by 3.7%.
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