The shock resignation of Martin Sorrell as CEO of the world’s largest advertising group WPP offers a stark commentary on the seismic forces facing the industry, even if the immediate motivation was an internal investigation into alleged misconduct. Clearly that explained timing of the resignation, which looked more like a two-fingered rebuff to his own company for daring to question his behavior as the architect of the remarkable WPP empire. The group molded by his sheer energy and force of personality is now likely to lack the cohesive force that has bound it together and disintegrate into its constituent parts. Yet these are mostly strong competitive businesses incorporating state of the art technology and likely to be worth at least…