The joy of The Secret of Chimneys emanates from its supporting cast – the witty and indefatigable Champagne socialist Lady Eileen Brent, the browbeaten Lord Caterham, the hapless Bill Eversleigh, even the overbearing, purple-faced politico George Lomax plays his part with aplomb.

In The Man in the Brown Suit Christie presents us with another plucky heroine, this time in the form of Anne Beddingfeld. Beddingfeld is one of Christie’s strong women, ready to weaponise her beauty and intellect, rather than subordinate herself to her patriarchal ‘protectors’.

The Murder on the Links contains a number of features that were to become Christie tropes – the watch with the broken face; the use of disguises; and the desire of a murderer to repeat their crime.

It is virtually impossible to describe The Secret Adversary without using the word ‘romp’, and it’s clear that Christie enjoyed writing this story.

Awash with red herrings and a cornucopia of clues, this book acts as a form of ‘preface’ to the stories that were to follow, introducing the reader to those elements that would become quintessentially Christie.