I didn't mean to carry out this experiment - it just came to me - but it certainly was interesting.
I was doing one of my modestly entitled Secrets of Success talks, this time at the excellent St Bede's School in Cambridge.
I was wonderfully looked after, not least by the headteacher, and head boy and girl - thanks all for a great session.
Anyway, one of The Secrets is - ***** spoilers alert here ***** - the importance of having faith in yourself.
There must have been 150 young men and women in the audience.
I explained how people often doubt they should be in the position they are, doing the job they do - the dreaded Impostor Syndrome...
How they can secretly believe they're not up to it, that they can't do what is expected of them, that they're going to be found out and fail...
And on a whim, I said, Put up your hand if you've suffered from Impostor Syndrome.
About half the group did.
So I waited a few seconds...
And then put up my hand too.
Which, interestingly, prompted just about everyone else in the hall to raise their hands.
Before you ask - no, I wasn't just playing along. Trying to make them feel better.
I really do suffer with the darned thing.
Whenever I stand up in front of an audience, whether it's to teach, or do a book talk, or chair a panel, at Cambridge University, or a writers' festival, wherever or whatever...
That little voice whispers its poison in the back of my mind.
Who are you to do this? Who do you think you're kidding? Go find someone else who can do a proper job of it.
But here's a funny thing.
Strangely enough, I've come to welcome the voice now.
It helps to fire me up. To make sure I perform as well as I can. To prove it wrong.
Which is exactly what I told the group at St Bede's.
All the great people I've been lucky enough to meet and work with over the years, all those who have been honest...
They all admit to suffering Impostor Syndrome at some point.
Which has led me to believe it's a part of us, a piece of what makes us human, designed maybe to make sure we never get complacent.
And that, in turn, has led me to this conclusion -
The trick is not trying to banish the infamous, insiduous, ineffable Impostor Syndrome.
The trick is learning how to handle it.