Martin Sorrell has resigned from WPP, the marketing group that he founded in 1985, leaving behind many wealthy executives. His largesse is reflected in the 400 companies that WPP lists as subsidiaries, the 43 small agencies that it bought last year alone, and the ￡13bn of goodwill on WPP’s balance sheet.

Wire and Plastic Products, the company he used for the longest acquisition spree in advertising, was not in the business itself. Sir Martin used it to buy everything from J Walter Thompson to Young & Rubicam and to defy the broader trend against holding companies. WPP held any agency going, apart from those acquired by Publicis, Omnicom and other rivals.

Many people in advertising regard themselves as creative — there are “creative data analysts, creative media buyers, creative media planners,” Sir Martin explained recently. But they are most creative at rewarding themselves by founding boutique agencies, selling to WPP and others, waiting a few years until their acquisition earn-outs expire, and then starting again.