Poacher turned gamekeeper or gamekeeper turned poacher? That depends on how you regard the related but different tasks of running a business and advising those who do. But slipping out of the professional service world to take up the reins of a corporation does at least provide an unequivocal retort to those clients who cry: “If you’re so smart, how come you aren’t running a business yourself?”

There are more former consultants working permanently in boardrooms than you might imagine. Jonathan Schwartz, the pony-tailed, blogging chief executive and president of Sun Microsystems spent part of his early career at McKinsey.