About twenty years ago, Alice Sherwood discovered that one of her friends was an impostor. At first, the lies he told were the usual Walter Mitty fantasies favoured by sad, deluded men – that he was working for MI5, that he was an aristocrat, that his father had been murdered – but they soon developed into something more dangerous. He got engaged to two women at the same time and stole money from his business partners. Luckily for her, she escaped financially unscathed. It was this personal brush with fraud that provided the spur for Authenticity.

The book begins with a study of various colourful swindlers from history, ranging from Joseph ‘Yellow Kid’ Weil (who inspired The Sting) to Elizabeth Holmes, once touted as Silicon Valley’s first female billionaire but now facing jail time for bilking investors in her blood-testing company, Theranos. Sherwood seems