The jewel in Grey's crown is Procter & Gamble, the world's largest single advertiser with brands such as Dreft, Fairy, Head & Shoulders, Olay, Pampers, Pringles and Vicks. Other global players among its clients include Diageo, Hasbro, Mars, Novartis, Slim-Fast and Warner Bros. Overlapping clients include BAT, Pfizer, GlaxoSmithKline and Nokia.