A client has recently resigned as CEO of a successful digital media agency to make space to think through his next career move. Within days, he was getting calls from his network to come help out in a variety of capacities such as board director and consultant.

His response was disbelief. What could he possibly bring to the party? He didn't know their business. I asked him what these people thought he could bring. One comment summed up what he was unable to see - "I want you by my side as I build this business – in any capacity – as I know I will do better with you around."

Clear to his network (and to me) is his enormous ability to contribute to a wide variety of situations. He exudes calm confidence, a sharp mind and had empathy for the people he worked with. He values happy staff knowing the profits will follow. He is able to balance customer service, with quality product and increasing profits. He is a compelling storyteller and his staff love him.

This man has so much to offer in terms of experience and approach to leadership. But he is plagued by the idea that he doesn't know enough and he's on the edge of being found out. For him to step into these new roles asked by him of his network makes him feel like an imposter.

This imposter syndrome is commonly found in high achievers. The achievement bar becomes confounded with perfection and fear of failure. The imposters' attribute their previous success to external factor as explained by the psychologist credited for naming this syndrome is Pauline Rose Clark.

"Even though they are often very successful by external standards, they feel their success has been due to some mysterious fluke or luck or great effort; they are afraid their achievements are due to 'breaks' and not the result of their own ability and competence."

I've experienced the imposter syndrome at various points in my career. In my last role as an industry technology analyst, I experienced crippling self-doubt when I had to present as the 'expert' on a trends at a conference. Was I really the most knowledgeable person in the room on this? I always waited for some killer question from the audience that would expose me. It never came but that didn't dispel my feelings of being a fraud.

As a coach, I see this imposter syndrome really kick in for people when they make big shifts in their career. Stepping into that new, challenging role highlights the insecurities over what got them to that place in the first place. They become certain that their luck will run out and they will be exposed for the average person they believe they are.

As Betrand Russell puts it so beautifully: "The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt."

In my view, the imposter syndrome feeds off our deification of data and 'doing'. We measure our value and contribution based on hard output. Whilst there is nothing wrong with that approach, it is an imbalanced view on what we can contribute. As we move up in the management layers, it becomes less about output and more about influence, collaboration and communication. And here many of us come unstuck because how to we measure the 'value' of these skills? It becomes even harder to feel confident in your contribution if it doesn't have a neat label like Java expert or Prince 2 consultant.

What helps is to talk about our own experiences. When I share my imposter moments with mentees or colleagues, they laugh at the idea that I would see myself as a fraud. Then many sigh, and share their own experiences. By talking about it, we create space for others in the struggle. Voices like Alicia Lui all contribute to normalising this.

You can be certain that in your team there will be staff that suffers from this syndrome. It's likely that they mask it well. You will spot it in others when they resist terrific opportunities like a cool project requiring new skills, or a promotion upwards. Dare to have the conversation with them.

The imposter syndrome is allowed to persist in our high-performing culture because we don't talk about it. It's time that we start being more open about our internal experiences for the sake of our staff and our colleagues.