At a party some years ago, Prior experienced a severe panic attack when faced with the daunting task of making small talk with strangers. ‘It was as if someone had spiked my drink,’ she writes. ‘My limbs were growing rigid and my smile was the tight rictus you see on the faces of young ballet dancers … Sweat was trickling down the insides of my arms.’ Fleeing the party, she determines to find out more about shyness in order to write an article or book about the condition.

Prior, ever the journalist, prepares a focused list of questions. ‘What exactly was shyness? ... Was shyness the same as introversion? ... Was shyness born or bred, or both?’ And then, more tellingly, ‘Why was I still fighting this battle after all these years? And why did it matter so much to me?’ Prior’s quest is therefore not simply rhetorical but a personal and anguished search for self-knowledge and identity. ‘Sian-ness’, as she admits herself, sounds a lot like shyness. ‘Shy … a timid little word that begs to remain unnoticed. Only three letters long and it begins with an exhortation to silence: shhh.’

She reads widely, interviews psychologists and scientists, finds fellow sufferers who share their experiences, investigates the biological and social reasons behind shyness. She also reveals much about her journey from ‘Shy Sian’ to ‘Professional Sian’.

Prior’s father drowned in the year of her birth. Despite a loving relationship with her mother and stepfather, Prior keenly feels the loss of a parent who, it transpires, was also shy. Her mother, a psychologist, recognising the signs of a withdrawn child, helped and encouraged her. Her shyness appeared more pronounced because her elder sister was an extrovert. Prior depicts herself at secondary school as tall, awkward, and androgynous-looking, desperately wishing to be noticed and to make friends, yet shrinking away from attention. These conflicting push-me, pull-you emotions plague her for years.

Until she discovers sex. Relationships provide much-needed security. She can want and be wanted in return, without the scrutinising gaze of society. Nevertheless, there is a degree of rescuing behaviour towards her lovers. Her first boyfriend is agoraphobic – she launches a campaign to rehabilitate him. Years later, she meets ‘Tom’, her great love, whom she weans successfully off heroin. Through helping her men, she is clearly trying to help herself.

Prior candidly examines the apparent dichotomy she displays between a life in the public eye and the agonies she experiences in social settings. She explains that she is an expert in adopting personae, and ‘Professional Sian’ is more than willing to interview the famous, make speeches, host political debates. For someone who fears rejection, collective praise is empowering. Still, she faces a furore because of an article she wrote about Julia Gillard. Gillard had described herself as shy, and Prior’s opinion piece described that admission as a sign of weakness. Now she recognises the article was more about her own response to shyness than about Gillard herself. But Prior takes such criticism on the chin: she has no wish to be invisible.

Yet when she returns to the home she shared with ‘Tom’, after their breakup, she removes the mirror beside their bed. Some people suffer from catoptrophobia, a fear of the reflections within mirrors. Carrying the mirror away, Prior wonders if there is a term to describe ‘a fear of the reflections to be found in mirrors that no longer reflect you’.

Prior invested much in this failed partnership, and Shy is an attempt to put the record straight after being sidelined by a man who no longer wanted a monogamous relationship. Despite meticulous and intriguing research into social anxiety, it is the arc of this affair that remains the fulcrum of the book. Prior’s style is fluid and confident, switching from Q&A to scientific analysis, reminiscence to interior monologue. She writes with great sadness about her post-breakup trauma, and here there is passion and poetry.

It is common knowledge that Prior was musician Paul Kelly’s partner for ten years, yet she insists on calling him by the pseudonym, ‘Tom’. Why such coyness? Prior explains that this is her story, not his, and that Kelly’s fame could detract from her account. But this seems a spurious argument. By not naming Kelly, Prior is evading a reality that would see her reflected compellingly and indelibly in that fickle mirror.