Sir Martin Sorrell is in trouble. The 73-year-old CEO OF WPP is under investigation for “personal misconduct” and “financial impropriety”, that he misused company assets.

To be fair, the independent counsel conducting the investigation said in a statement that, “The allegations do not involve amounts which are material to WPP.”

Sorrell has rejected the accusation.

Sorrell formed WPP in 1985 after leaving Saatchi & Saatchi where he was head finance officer. At the time, it was a shell company called Wire & Plastic Products. Sorrell turned it into a marketing services group in 1986. By 1989, he had acquired JWT and Ogilvy & Mather. He has been chief executive of the company for more than thirty years, many of those have been good ones, despite an annus horribilis in 1990 during the GFC. WPP now has now has 3,000 offices in 112 countries.

Last year wasn’t. Growth was flat, although profits were more than £2bn. And its share price has been falling in the last twelve months from £17.31 to close at £11.17 (down almost 40%).

With a personal stake in WPP of about £250m, Sorrell is still inordinately wealthy. His payouts have both ignited envy and raised eyebrows. A £70.4m payout in 2015 was one of the biggest pay deals in UK corporate history. But more than a third of investors refused to back it. Sorrell’s governance of WPP and his refusal to undergo succession planning have been subjected to some challenge in recent years.