Account was won following a competitive pitch.
Ahmed founded the business in 1994. It was acquired by WPP in 2012.
Brett Marchand will be interim group chief executive.
The move comes as Roblox is accused of failing to protect children from harmful content.
Campaign asks adland’s brand marketers on the value of individual ad shops.
Elon Musk’s 'free speech' social platform discloses its content moderation practices.
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