With each step I am more certain,” Julie Andrews sings to herself as she marches into her first job as a nanny in The Sound of Music . “Everything will turn out fine. I have confidence the world can all be mine, They’ll have to agree I have con-fi-dence in ME.”

All my working life I have tried to emulate this attitude. If only I could muster some “con-fi-dence in ME”, the world would be mine, too. I never bothered to ask if this approach was right because obviously it is. Everyone admires people who are confident. Everyone wants to instil confidence in their children. If I look at one of mine – who was born believing that he was a thoroughly good thing – it is perfectly clear to me that he has won the genetic jackpot.

Even people who do not take The Sound of Music as seriously as they ought to agree that confidence matters. When Michelle Obama (who has inexplicably said she prefers It’s a Wonderful Life to The Sound of Music) visited an inner-city school in London a few years ago, she told the students: “Your success will be determined by your own confidence and fortitude.”