That being the case, no-one believed he would keep his head below the parapet when WPP's Italian operation was engulfed by scandal. And he did not disappoint, going on radio to express his anger and sending a signal to shareholders of his determination to root out any wrongdoing.
His decision is courageous. Who knows what may emerge as investigations proceed into claims Marco Benatti, one of WPP's senior managers, was paid for introducing a media buying company to WPP without disclosing he was an investor in it. Benatti, who is now taking legal action against WPP, denies all allegations of impropriety.
What is more, Sorrell will have known exposure of the scandal would undoubtedly draw media attention to his relationship with Daniela Weber, WPP's chief operating officer in Italy and an associate of Benatti for more than 20 years. But he will have been equally aware keeping mum was never an option. WPP's Italian interests may account for less than 3 per cent of WPP profits, but the scandal could have far-reaching consequences unless contained.
There is certainly much at stake. Indeed, shareholders might reasonably ask, if financial scandal can strike in a sophisticated market such as Italy, how much more likely is it to happen in the developing markets of the Far East, where WPP is busily extending its activities. In opting to clean out the stables, Sorrell has to convince the investment community that Italy is a one-off.
The fact he has acted swiftly and decisively should ensure his and WPP's reputation for integrity remain intact. But the affair does pose the question of whether the group is now outgrowing the hands-on management style of its mercurial chief executive.