Martha Stewart says her three greatest character flaws are impatience, being too forgiving and not being forgiving enough. Pierre Yves Gerbeau declares that his greatest weakness is being “brutally honest”. Barbara Stocking, head of Oxfam, describes her worst failing like this: “I move too fast.” And David Giampaolo of Pi Capital has shortcomings that are the most sick-making of the lot. He is, he says, “too trusting and too accessible”.

Every week for the past year and a half, the Financial Times has asked business leaders 20 questions including: “What are your three worst features?” By studying the replies I’ve amassed a treasure trove of data that overwhelmingly support a long-held pet theory of mine. The three worst traits of chief executives are a lack of self-knowledge, a lack of self-knowledge and a quite extraordinary willingness to give themselves the benefit of the doubt.

When it comes to describing their dark sides, 58 out of 60 leaders felt bound by the same rule: any weakness is perfectly admissible, so long as it is really a strength. They almost all cite impatience, perfectionism and being too demanding – all of which turn out to be things that it’s rather good for a CEO to be.