Thornell conjures a chivalrous Australian admirer with a passable English accent, and deploys Christie’s seemingly inexhaustible supply of stereotypes to give authenticity to his tepid romance with Agatha. Christie readers will be reminded of Katherine Grey in The Mystery of the Blue Train (1928), the novel that Christie was agonising over around the time of her disappearance, and will not be surprised that Thornell’s heroine has an alternating skittish, languorous, and distant gaze. Those less tolerant of Christie’s idiosyncrasies, may find that Thornell’s ‘piquant’ ladies, ‘well-tailored’ frocks, ‘irreproachable tweeds’, elderly couples who wear their age ‘rather pertly’, and the ‘most respectable roast beef sandwich’ overstate the trademark.

On the Blue Train shares a creative female protagonist restricted by her social milieu with Thornell’s first novel, the Vogel Award-winning Night Street (2010), a study of the artistic, emotional, and sensual life of painter Clarice Beckett. I have always suspected that Christie in person would have been far less amusing than her work, and wonder whether Thornell was hampered by that realisation. Nevertheless, as Christie has provided me with decades of entertainment, I had hoped for something more intriguing for Agatha than a guilty admission of desire, a stumble into an embrace, and one illicit kiss.