Like it or not, Wire and Plastic Products (WPP), the world’s former biggest advertising group, is heading south with the speed of a falling meteorite. The rainclouds of misfortune thickening against it cannot point to anything but a long-foretold unravelling. First was the April 2018 disgraceful ouster of its founder/CEO, Martin Sorrell after 33 years, following allegations of personal misconduct …