Ad agency WPP enjoyed its fastest growth in a decade in the last three months chief executive Sir Martin Sorrell said yesterday, as recovery in corporate earnings fed through into marketing spending. "Everything we see in the rear-view mirror is good," he told the World Retail Congress. "This quarter looks as though our revenues have pretty much got back to where we were in 2008, including TNS, but with 8% fewer people".Customers are also spending more on traditional advertising, rather than online, while the business cycle had moved from cost-cutting to investing. "2009 was about survival but 2010 is about top-line growth," he said. "There's a view that online is more about price promotion, traditional more about brand-building. It may be one of the reasons why traditional has come back a bit," he added.WPP, the world's largest ad and marketing group, lifted organic sales by 4% in the first nine months of the year, Sir Martin said, better than its own forecasts. Profit margins also rose over the same time last year.The group saw "sequential improvement through to September, with the exception of June", he added. WPP's North American business grew by 8% in the third quarter.The group formally publishes its third quarter numbers on Friday. Pre-tax profits in the half year to June rose by 36% to £244m on revenues 3% higher at £4.45bn. Billings were up 8% at £20.3bn. Operating profits rose by 33% to £455m with margins up by 2.3%.