Taken on its own terms, I think this is one of Christie’s strongest mysteries. It’s clever, well-written, populated with strong characters, truly devious in its construction and it features, almost as a cameo, a Jane Marple so clear-sighted and so fierce and remorseless that when I saw her knitting, I thought not of some nice old lady but of Atropos with her scissors, bringing final judgement.

In many ways, this is Christie at her best. She effortlessly makes the middle-class brother and sister, Jerry and Joanna, at the centre of this story engaging and energetic without needing to make them either perfect or particularly nice. She immersed me in the life of the notables in this very small town, bringing them alive through the dual lens of the reaction of the brother and sister as newcomers meeting people for the first time and through the gossip, sometimes solicited, often proffered as a sort of ‘welcome to our town’ gift to the young couple. Having established gossip as cherished currency in the town, Christie then adds the poison letters which slowly taint the atmosphere of the town like ink dropped into water. By the time the first death occurred, Christie had leashed my imagination and my curiosity and I needed to know who was behind it all.

The plot was twisty enough that I made no progress at all on figuring out what was going on but instead lurched from one moment of misleading clarity to another, following Jerry’s footsteps as he keeps involving himself in the police investigation.

I liked that the police were both smart and thorough and made steady progress but moved too slowly to keep everyone safe. So, in the final quarter of the book, the rather remarkable and I thought very likeable vicar’s wife calls in Miss Marple as ‘an expert in evil’. I loved that description.

Quietly and with the ruthless efficiency of a gardener dead-heading roses, Miss Marple sorted it all out. The solution left me slapping myself for not having foreseen it.

The main plot point that I disliked is that Christie once again insisted on introducing an insta-love scenario so that those who survived could live happily ever after. It was, I thought, unconvincing and unnecessary.

If I had read this when it was published in 1946 (and no, even I’m not old enough to have done that) that would probably be the end of my remarks other than saying that I much prefer Marple’s surgical dispassion to Poirot’s self-aggrandising method.

Reading it today though, I kept being distracted from the plot by my dislike of the values, attitudes and behaviour of the middle-class protagonists, especially Jerry, from whose point of view the story is told.

Jerry Burton is sexist. He assesses every woman he meets against a set of standards he seems to assume they should either have been built to or should be amending themselves to achieve. He is frightened of intelligent women who say what they think because it makes them disquietingly unpredictable. He treats the woman he is most attracted to as if she were a lost dog that he wants to take home and look after. His only solid relationship with a woman is with his sister and it seems to me that that works because he barely thinks of her as a woman at all. At one point, he physically grabs a woman significantly younger than him, whisks her away to London and indulges in what today would be seen as grooming. He acknowledges that his behaviour was ‘a little mad’ but sees no harm in it and admits to no fault in himself beyond being impetuous.

This would have been my major source of anger with the book had not been for the way Jerry and all the other notables in the book treated their female servants. These women are not seen as real people. They are lesser beings. They are treated like farm dogs, useful if they are biddable and well-trained. Those servants who try to use order and formality to define the standard of their work and to set clear boundaries between themselves and their employers are made fun of for being stuffy. The young ones are ridiculed for being ignorant as if being uneducated was their fault. Their lives or deaths are of much less consequence than those of any of the notables in the story.

I don’t blame Christie for any of this. I’m certain that she’s describing attitudes and behaviours that her readers would have recognised and accepted as normal. This means that what’s making me angry here isn’t Christie’s fiction but England’s history.

This is one reason why I disagree with HarperCollins’ Bowdlerisation of Christie’s text, which they are editing to remove anything that offends their ‘sensitivity readers’. I think it’s important to realise the contempt that women and servants were held in seventy-seven years ago, especially when it’s a time many of our leaders are eager to return to.