A few years ago, I was invited to take part in a panel discussion to celebrate female success. Sitting on stage, alongside some highly respected women, I began to feel as though there was a big sign flashing above my head: FRAUD.
I felt sure I was about to be found out; exposed as someone who wasn't as good as the others and didn't deserve to be there.
Oh, and the topic of that discussion? Imposter syndrome.
Until that day, imposter syndrome was something I thought affected other people. Now, after making a new podcast for the Telegraph, Imposters, I know it can strike anyone – no matter how successful or confident they might appear.
Not that everyone wants to admit it. After all, having any sort of psychological "syndrome" sounds terribly grand, doesn't it? Just who do you think you are? Or perhaps that's just our inner imposters talking …
At its most basic, imposter syndrome is the struggle to believe that you deserve your success as result of your hard work and experience. Instead, you attribute it to luck, fluke or being in the right place at the right time. You worry that everyone will eventually realise this, whereupon it will all come crashing down. It goes hand-in-hand with perfectionism. If you're the sort of person who sets unrealistic goals for themselves and then self-flagellates when you struggle to meet them? That's just imposter syndrome in disguise.
The term was coined in 1978 by psychologists Suzanne Imes and Pauline Clance, who called it the "Imposter Phenomenon" (which some academics still prefer as IS hasn't been officially classified as a mental disorder, although low self-esteem and a feeling of failure are recognised as factors that can contribute to mental illness) and identified women as the sole sufferers.
Research has shown that both genders are affected, albeit women still tend to come out on top – academics remain conflicted over whether we are genuinely less confident in our abilities or just happier to admit to it. In a 2018 study of 3000 UK adults by OnePoll, 66 per cent of women and 56 per cent of men said they had experienced imposter syndrome over the previous 12 months. Other surveys have placed the number of women suffering at closer to 90 per cent.
Now, as uncertainties around the return to the office continue, that number is predicted to rise further. The dislocation and isolation of working from home, the challenges of communicating virtually with our colleagues and anxiety of being out of our comfort zones during the pandemic have all contributed to an epidemic of self doubt in Britain's workforce. During this slow and frustrating return to normal, more of us than ever are feeling inadequate.
"Lockdown has had an impact in terms of imposter syndrome, as you don't have the same opportunity to bump into people making a cup of tea or go for drinks," explains Dr Jessamy Hibberd, psychologist and author of The Imposter Cure.
"It leaves less room for being reassured in terms of how you're doing with work or getting the feedback you'd normally have in an office environment.
"Working from home you also don't have the same chance to gain perspective, so you can start to worry about something and then it gets bigger and bigger – but you're not then seeing anyone who can give you a different view."
Nor will the effects of WFH just disappear the moment we set foot back in the office, adds Dr Hibberd, who calls our homes "a breeding ground for insecurity and self doubt".
"The cumulative toll means that moving out of the bubble you've created around yourself to get through this period can seem quite daunting," she adds.
No one has been more surprised by this resurgence than "Imposter Phenomenon" pioneer Dr Pauline Clance.
"I am surprised that the concept is now so prevalent. When I wrote my book, I thought there would be an audience. I certainly did not think ahead to now," she tells me.
"Certainly the pandemic may have made people feel more on their own and that may contribute to imposter feelings."
Women, Dr Hibberd thinks, will be particularly prone to this post-lockdown imposter syndrome because of the disproportionate domestic pressures that have been placed on them.
"Somebody said to me recently, 'I don't know why they think I've been doing a good job, I've been doing the school pick-up every day'," she says.
"It made me think of the rules imposters have: they have one rule for when things go well, which is that they then put that down to external circumstances. And then if things go badly, it's a personal failing. So then no matter how well you're doing, you're not taking it on board."
That certainly rings true for me. But what if, by giving voice to those rules and understanding that we feel that way sometimes, we could start to take away some of the power imposter syndrome holds over us?
It's why I set out to demystify it, interviewing six women who have carved out amazing careers in challenging – and often male dominated – industries. And guess what? Each suffers with self doubt. Sometimes it manifests itself as crippling fear, leading them to miss out on exciting opportunities – such as the time June Sarpong, TV presenter and BBC Head of Diversity, hid from a fellow famous person she was longing to meet or the day she sat next to someone she was desperate to interview but didn't ask.
For others, like Samantha Cameron, it is more subtle – the sort of traits she wouldn't label as imposter syndrome but prefers to call being "self critical" and a "perfectionist".
Trinny Woodall puts it down to letting herself burn out and, critically, not backing herself, telling me a story about over-preparing for a speech, with hundreds of slides and notecards, when really the knowledge was all in her head – and the very reason she had been asked in the first place.
More than one woman told me that she had got to the top of her field by "luck", including Clare Smyth – the first British female chef to win three Michelin stars – who worries that she could lose everything tomorrow.
"There are times where I think that maybe I'm not as good as the other people think I am, or maybe that I'm lucky," she admitted.
Luck also reared its head when I spoke to Holly Ridings, over Zoom from Texas. Holly is the most exceptional woman you've never heard of: it's her job to put the second ever group of astronauts (including the first woman) on the moon in 2024. She hasn't so much broken the glass ceiling as smashed through the Earth's atmosphere. You can see why she might be daunted from time to time, but as Nasa's first female chief flight director – a role she took on in 2018 after 20 years working at Kennedy Space Centre – she still told me that she had "won" her job.
One woman I wasn't sure would have imposter syndrome is Priyanka Chopra Jonas: Bollywood superstar, Hollywood A-list, entrepreneur, author and producer of acclaimed Netflix drama The White Tiger. She has a CV someone twice her age would be proud of but she still has an inner critic; that voice in her head that she said makes her think: "Oh, my gosh, am I not good enough for this job? Or am I not good enough for this dress? Or am I not good enough for this position?"
Doesn't that sound familiar? Turns out you can star in more than 60 films, win 35 awards, announce the Oscars – and still feel as though you're not enough.
"The higher you get, there's also a part that comes in terms of 'well, I've got further to fall'," explains Dr Jessamy Hibberd.
"And this idea that there are more eyes on you … it's like 'well now it's going to go really wrong'. So the fear can even get greater."
The trouble is, she adds, that there's often a grain of truth in our reasons for feeling like imposters.
"Luck does play a part, or timing, or working hard – but all the other things have got to be there together as well. Loads of people have good luck, loads of people have good timing, but they make nothing of it. Even something like working really hard – anyone can work really hard, but most people don't. It's the way that you see those skills and the contribution they make towards it [your success] and how much ownership you take - and most people don't take ownership."
So how do we stand up to imposter syndrome when it strikes?
My interviewees opened up about their techniques – the things they do behind closed doors, before they put their public face on and go out into the world.
For June Sarpong, the lightbulb moment came when she named her imposter syndrome "Agnes". Whenever "Aggie" threatens to take over, she can address her directly and tell her where to go.
For Priyanka Chopra Jonas, the answer is to talk to close friends about it.
"I visualise it like a balloon, [and] it just starts becoming bigger," she says. "And as soon as you talk about it, it's like putting a needle in it. It just takes away the power."
Samantha Cameron advocates taking it one day at a time.
"I've been through really… challenging periods in my life, and you've just got to go, 'I've got to get through today'," she told me.
"Set that little goal, achieve that, [then] not look too far ahead if it's a bit scary … sometimes looking at the big picture and worrying too much about the future can be really overwhelming."
"The key thing is having more transparency, making sure that you're talking to other people," says Dr Hibberd.
"The other big thing is to externalise your imposter voice, so you're not seeing it as your own voice but the voice of your fears. And then it gives you the chance to challenge it rather than just go along with it. So if the imposter voice says 'you won't do well at this unless you work all weekend', you can reply 'Okay that's my worry but what's the reality?' It's that idea of not basing it on a feeling, but basing it on factual information."
She advises making an emotional CV of your achievements.
"Start to pay attention to things that are going well and writing them down, or looking back at your experiences and what's gone well," she says.
"So that you've got a chance to take it on board and see it as part of you, rather than fluke."
Listen to the first episode of Imposters, in which Trinny Woodall discusses how imposter syndrome has caused her to burn out and severely doubt her own knowledge – and what she did about it, today at www.telegraph.co.uk/theimposters