'I'm a chemist - Agatha Christie wrote one murder plot better than any other'

Daily Mirror

17-06-2025

A new book, V for Venom, by a chemist-turned-author Kathryn Harkup reveals why Agatha Christie 's poison plots were so accurate – and why we still can't get enough of a good cosy murder mystery story
There's nothing the British public enjoys more than a good murder – on TV, of course! Whether it's re-runs of Hercule Poirot, brilliantly played by David Suchet, Miss Marple, or Angelica Houston in the new BBC Agatha Christie adaptation Towards Zero, everyone loves a good murder mystery.
Queen of Murder Dame Agatha Christie is probably the best-selling author of all time. Churning out 66 detective novels and 14 short story collections, she also wrote the world's longest-running play, The Mousetrap. And her stories have been made into at least 23 films, including Death On the Nile and Murder On The Orient Express, as well being adapted into numerous TV series.
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According to a new book, among her many, imaginative ways of 'doing in' her victims, poisoning was a favourite choice,
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Kathryn Harkup, author of V is Venom: Agatha Christie's Chemicals of Death, says it was her use of poisons - both to add intrigue to plots and to murder victims with - that put Christie head and shoulders above other writers during the Golden Age of detective fiction.
'Christie did use an awful lot of guns, stabbing, blunt objects, strangulation to kill her characters – she went through the entire range,' says Kathryn, 47, of Guildford, Surrey. 'But I think she is exceptional in her use of poisons, because she was a chemist and also such a prolific writer that she used so many different examples in her books.'
Born in Torquay, Devon, in 1890, Agatha Christie volunteered during the First World War as a nurse and later trained as a dispenser.
Drugs didn't come ready packaged in those days, says Kathryn, they had to be measured, mixed together and processed, according to doctors' prescriptions.
And her dispensing experience was clear in Christie's writing, as she always quoted quantities of poisons in grains throughout her stories, as she was not a fan of the modern measuring system.
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'The great danger of the metric system', she said, 'is that if you go wrong, you go 10 times wrong.'
It's more than a century since Christie wrote her first novel, The Mysterious Affair At Styles, which she penned in 1916 but was published in 1920.
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Many of her novels were written in the 1930s – a decade that, in our collective imagination, is synonymous with the author.
Kathryn writes: 'The world Christie created is perhaps a little more detached from horrible reality than others. But, again, many other writers have done the same, blotting their charming chocolate-box sceneries.'
She quotes US writer Raymond Chandler, who said: 'All crime fiction has to have an element of detachment from the real world, otherwise, it would only be written and read by psychopaths.'
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Kathryn feels Christie expertly wove the glamour of decades like the 1930s into her gripping murder plots, to draw readers in.
And her attention to detail when setting the scene is what has made her appeal so enduring.
She adds: 'I think there is this huge nostalgia for that era (the 1930s) with all these beautiful clothes and cars and gorgeous art deco buildings – even though Christie was writing books right into the 1970s. When you read her stories she is much more contemporary when writing.
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'However it's the backdrop of glamour that increases our detachment from the horror of what is a murder. So you can just sit there and enjoy it as a puzzle and have a nice afternoon on the sofa with a cup of tea and read about a gory murder.'
A trained chemist, Kathryn is endlessly impressed by the accuracy of Christie's use of poisons in her plots - although, readers can breathe easy, as many of the toxic tinctures she uses are no longer available.
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She says: 'What has changed since the 1970s is accessibility – you just can't get hold of the stuff that Christie's writing about very easily.
'Also, methods of detection are far, far superior these days, as well as medical treatment. People who are poisoned are much more likely to survive. And so you have attempted murder rather than actual murder.'
Historically, poisons were a very popular way to kill people off, as these kind of homicides were so difficult to prove. Many killers got away with murder for years.
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Kathryn explains: 'It was in the Victorian era that people decided to do something about this and establish some protocols and some tests that can find these poisons and show evidence to a jury.'
She also cites infamous trials in the past where murderers were clearly inspired by Christie – and tried to get away with their crimes.
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'In 1977 there was a case of atropine poisoning in France,' says Kathryn. 'As soon as they raided Roland Roussel's flat they found a copy of Christie's book, The Tuesday Murder Club, with heavy underlinings and the spine broken on the appropriate page.'
The case of the Hay Poisoner in 1921 also had all the ingredients of a Christie murder mystery story, when a respectable Hay-On-Wye solicitor Major Herbert Rowse Armstrong was found guilty of murdering his wife Kitty with arsenic. Nine months after his wife's death from supposed gastritis, heart disease and inflammation of the kidneys, her body was exhumed after her husband was accused of poisoning a rival solicitor.
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Police found her corpse with arsenic, and when police arrested the Major they discovered a twist of the same poison in his pocket, which he claimed he used to control dandelions in the garden. Major Armstrong was sent to the gallows on May 31, 1922.'But the most recent is probably serial killer Graham Young, also known as the Teacup Poisoner, who was convicted several times for poisoning people, but in 1972, was locked up for murdering his victims with thallium.
'It was a very prominent case and Christie got mentioned in the actual trial because they thought she might have inspired him. Although, to be fair, Young didn't need inspiration, he was well and truly down that path already.'
While incarcerated in Broadmoor, the tale took another murderous twist, because one of Young's fellow inmates died of cyanide poisoning. Young had been heard many times saying how cyanide could be extracted from laurel leaves, and as it was noted, the grounds around the psychiatric institution were covered with laurel bushes.
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In fact, you'd be surprised how many plant species in the UK are absolutely toxic, such as yew tree, foxglove and the cuckoo pint, along with those which have have suitably evil sounding names such as poison hemlock and deadly nightshade.
Which must make a walk in the countryside very worrying for a chemist. 'I do walk past things like cow parsley and wonder, 'Oh is that cow parsley or is it hemlock, because they look very similar.'
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And she tells the story of how she went into a cafe – and went pale when she saw the flowers they had used to decorate the counter. 'The cafe had fresh flowers on top of their little cake display counter and one day I went in and they had monkshood in the vase. I asked the person behind the counter if they were real, and she rubbed her fingers on the leaves and said, 'Yeah they're real.'
'You can absorb that stuff through your fingers, but you've actually got to eat it to be dangerous. However monkshood shouldn't be put that close to food.'
And there are many everyday foods we eat which could kill us if we ate them in large enough quantities.
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'Sweet almonds are fine, but bitter almonds contain cyanide,' says Kathryn. 'I was once doing a panel once and a man got concerned because he loved marzipan and liked to eat chunks of it.
'I could see him just getting paler and paler as I described the use of almonds. So, to reassure him, I worked out the lethal dose of marzipan, which was about the size of a Labrador – plus you'd have to eat it all in one sitting.
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'Apple pips and cherry pips too – they contain cyanide,' she adds. 'I also worked out the lethal dose of apple pips, it's about 200 grams. And you'd really have to crunch it up, because the cyanide compound is inside the pip and it's protected by a tough coating.'
Christie also had ingenious ways in her books of making sure the right person was poisoned.
'She would pick a particular food item that only one person at the table likes, or is likely to eat. For example, in her book, A Pocketful of Rye, the person that they want dead is the only person who's going to eat the poisoned marmalade.
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'And, of course, there were also antidotes, so the murderer could save themselves later.'
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But Christie herself was also inspired by one of our earliest and most famous true crime murder cases. Dr Crippen poisoned his wife Cora in 1910 with hyoscine then dismembered her body, and Christie based her book The Moving Finger on his crimes.
As someone who is herself an expert on poisons, Kathryn revealed how she would use one.
'I would go into a very detailed history of their medical conditions, their dietary habits and I would tailor it to them, because the thing you've got to avoid is an autopsy,' the author muses. 'Forensic toxicologists are phenomenally good at their job. You've gotta mimic natural causes, because if it goes to the autopsy stage, it's game over.'
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Lucky, while the science may be accurate, her poison plot is purely fictional!
• Kathryn Harkup's book V is for Venom: Agatha Christie's Chemicals of Death is published by Bloomsbury on June 19
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Agatha Christie's library of poisons
Anthrax - infection caused by Bacillus anthracis bacteria which is found naturally in soil
Arsenic - naturally occurring metal element known for its toxicity
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Cyanide - extremely poisonous toxic liquid
Curare - plant-derived poison known for causing muscle paralysis
Gelsemine - highly toxic plant derivative that can cause death
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Nitroglycerin – a type of nitrate that relaxes blood vessels but too much causes death
Ricin - chemical poison which can be made from waste material left over from
Strychnine - white, odourless, bitter crystalline powder and strong poison