S ir Martin Sorrell’s digital advertising firm S4 Capital has enjoyed boosted profits, as the boss said its clients’ focus on performance amid forthcoming global recessions will “play to our strengths”. The company reported its gross profit and net revenue reached £250 million in the three months to September 30, up 73% on a reported basis from the £144 million posted this time last year. Revenues also surged by more than two thirds on a reported basis, from £178 million last year to £300 million in the latest quarter. Sir Martin said that the firm has kept up momentum despite…