The Hay Poisoner Transcript

Caroline: On 26 October 1921, a solicitor named Oswald Martin went to have tea with a fellow lawyer named Herbert Armstrong. The two worked for rival law firms in the town of Hay on Wye, which lies on the border between England and Wales. They were currently representing opposite sides in a local property dispute, but everything seemed amicable to Martin, and he chatted with Armstrong as they enjoyed the cake and scones Armstrong’s housekeeper had laid out.

At some point during the meal, Armstrong picked up a buttered scone and handed it to his guest to eat, asking Martin to “excuse fingers”. Later that day, Martin was taken very ill with what at first seemed to be a bilious attack, although he later developed a worryingly rapid pulse rate and a local doctor was called in to treat him.

It later turned out that during his tea with Armstrong, Martin had consumed a hefty dose of arsenic. His subsequent illness set in motion a train of events that led to an exhumation, an infamous trial and, eventually, an historic execution. The case was hailed by George Orwell as a grisly highlight of Britain’s “Elizabethan period” of murder, and it went on to exert great influence over crime writers working in the 1920s like Dorothy L. Sayers and Anthony Berkeley.

After all, isn’t a poisoner handing his victim a scone laced with arsenic during a genteel tea party just like something out of a golden age murder mystery?


Welcome to Shedunnit. I’m Caroline Crampton. This is another instalment in my irregular series about the real life crimes that inspired the writers of classic detective stories. Today we’re going to learn all about Herbert Rowse Armstrong and how his adventures with arsenic in the early 1920s ended up being immortalised in fiction.


There are so many aspects of the Armstrong case that seem to be lifted straight out of the pages of a 1920s whodunnit that it can be difficult to remember sometimes that the whole tale wasn’t constructed by a novelist for our amusement. Tropes that we’re so familiar with from detective fiction just keep surfacing. Probably the most obvious of these is to be found in the character of Armstrong himself. As well as being a solicitor, he was a church warden and a freemason, a well known and well liked addition to the town of Hay on Wye. He was married and a father of three children. As neighbours, strangers and journalists alike said after his trial, it would be hard to find a less likely murderer. Armstrong’s unlikeliness was even discussed by the characters in a real life detective novel, Detection Unlimited by Georgette Heyer, published in 1953. “Armstrong was a respectable little man no one ever dreamed would murder anyone, but he did, so it’s no use saying the motive isn’t strong enough,” one says to another. In novels at least, it’s always the person you least expect. Isn’t it?

There were perhaps a few clues in Armstrong’s background to his eventual fate, if one is willing to play armchair psychologist for a second in the best tradition of of the amateur sleuth. Although by 1921 he appeared to be a model of middle class prosperity, he wasn’t born into financial ease. He was born in 1869 in Plymouth to a colonial merchant and his wife, and grew up there and in Liverpool where — as far as I’ve been able to find out — the family’s fortunes were decidedly on the wane by the time Herbert was old enough to think about a profession. The generosity of two aunts enabled him to go to St Catherine’s College, Cambridge to study law, and from then on he worked hard to achieve the kind of stability and social position that he hadn’t had as a child. Armstrong was also quite small in stature even as an adult, standing just over five feet in height and weighing around 7 stone. Both court reporters and later authors made much of this, suggesting that his lack of height and overt masculinity helped to make him into a murderer, but personally I’m not sure there’s much concrete evidence for that.

He moved to the Hay on Wye area in 1906, after successfully applying for a job in a law firm there, and a year later he married Katharine Friend. They had three children in quick succession, and in between work, parenting and church matters, Herbert also found time to take part in the Volunteer Force, a kind of proto Home Guard. That meant that when the First World War broke out in 1914, he was called up straight away. He served at various bases around the UK and was also deployed in France. He seems to have done well in the military — he had achieved the rank of Major by the time he was demobbed at the end of the war. He apparently liked to be called “Major” in civilian life afterwards, which is a fact that perhaps matches up with his lack of height and Poirot-esque moustaches in creating what became the public image of Armstrong as a shy, henpecked, status obsessed man with an inferiority complex.

I’ve talked a lot on this podcast about how the First World War was a great force for social change far beyond the battlefields, especially in relation to the roles and opportunities to women. Some men took advantage of the greater freedom and license the war years offered too, and Herbert Armstrong was one of them. Although his letters to his wife and children are affectionate, Armstrong, shall we say, lived it up during the war, starting a number of affairs and seemingly acquiring a taste for a secret life beyond his churchwardenly peacetime persona. Knowing this, with hindsight it’s not that surprising, then, that in 1919 his wife was suddenly taken ill.


Amid all the publicity around Armstrong’s trial and what came after it, I think the sad fate of Katherine gets a bit lost in most of the accounts. In May 1919 she was taken ill with a mixture of symptoms including numbness, pain, headaches and gastric trouble. The local doctor, Thomas Hincks, was called in and diagnosed a kind of neuritis, which as far as I, as a non medical expert, can make out is a broad term given to a whole variety of problems that stem from nerve inflammation. After that initial attack, she recovered and didn’t see the doctor again for a year. But during the summer of 1920 she went downhill again rapidly, with her mental health affected too after weeks of being unable to get out of bed because of continual vomiting. Her doctor, apparently still not suspecting anything untoward, recommended that she go away for treatment at a private mental asylum called Barnwood.

While Katharine Armstrong was away, something rather extraordinary happened. A solicitor from another town in Wales was arrested upon suspicion of murdering his wife with arsenic. Mabel Greenwood had lived with her husband Harold and their four children in Kidwelly, a town about 70 miles west of where the Armstrong were based, until she died suddenly in June 1919 after a perfectly normal meal disagreed with her. Her husband Harold Greenwood then married another woman with what the local community considered to be unseemly haste, and there was a lot of gossip about whether Mabel had in fact been poisoned to make way for Harold’s new woman. This, too, to me sounds like something out of an Agatha Christie novel, but it really did happen, and after about four months the accusations reached such a pitch that the Welsh police actually applied to the Home Office for permission to exhume Mabel’s body.

It was found to contain about half a grain of arsenic, and so a year after she died her husband was arrested for her murder. It caused a great sensation in the national press mostly because of how rare it is for a member of the legal profession to be tried for a major crime like murder. The publicity was such that Greenwood was able to secure the noted barrister Edward Marshall Hall to defend him. Known as “the Great Defender”, Marshall Hall had a great reputation as a brilliant orator and was very popular with the press. His defence for Greenwood relied on the fact that the police had no actual evidence showing that he had administered the arsenic to his wife, and made much of the fact that the whole thing had only ended up in court because of slanderous local gossip. Marshall Hall also spent a lot of time casting doubt on the forensic evidence and refuting the contradictory claims of various servants. And it worked: Greenwood was acquitted in November 1920, while Katharine Armstrong was away being treated for her own mysterious complaint at the private asylum. After the trial, Greenwood changed his name to Pilkington and moved to a different town with his new wife and lived an apparently blameless life until he died naturally in 1929.

Katherine began to improve as soon as she was admitted to Barnwood. She was extremely weak when she arrived and was experiencing serious symptoms like heart murmurs, but after about four months there she was well enough again to be discharged to be cared for at home. She arrived back at Mayfield, the Armstrong house near Hay on 22 January 1921, her apparently husband having driven to Gloucester to fetch her. Almost immediately, her mysterious illness returned and, weakened by the previous bout, Katherine went downhill quickly. Dr Hincks was puzzled as to why she should recover so positively at the clinic, only to relapse so utterly when she got home. Her husband was seemingly very concerned too, spending long hours by her bedside. Exactly a month after getting home from Barnwood, Katharine Armstrong died at home from her symptoms. Her death was recorded by the doctor as being caused by gastritis and heart disease and she was buried with all due ceremony. Nobody suspected anything.

At least, not yet.

After the break: how that scone triggered a murderer’s downfall.

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In Unnatural Death by Dorothy L. Sayers, her sleuth Lord Peter Wimsey tackles a very difficult case. He has plenty of reason to suspect that a murder has been committed but absolutely no way of proving it or even really investigating it in any meaningful way. Wimsey and his friend, the Scotland Yard inspector Charles Parker, discuss this endlessly throughout the book, wondering whether it’s really only the bad murderers who get caught. The ones like George Joseph Smith of “brides in the bath” fame that I talked about on episode 21 of this podcast who don’t seem to be able to stop once they had got away with a few times. Sayers’s novel was published in 1927, and she has Wimsey explicitly reference Herbert Armstrong a couple of times, as another example of someone who might have got away with their initial crime if they had only had some restraint. The serial murderer is such a staple of crime fiction, and Sayers uses it to great effect in this book, as her initial culprit commits more crimes as they try to thwart the investigation and get away with the initial killing.

If Herbert Armstrong had laid low after his wife’s death, he might have escaped detection altogether. Unlike in the Greenwood case, it seems that there was little or no speculation that Katherine had been poisoned in his town. Later, it did emerge that Herbert had a “lady in Hampshire” to whom he had proposed marriage in the aftermath of his wife’s death, but this wasn’t well known and there was no community outcry. He continued to practise law in Hay on Wye and live at Mayfield. Two of his children were away at boarding school but the youngest still lived at home, and there were three servants in the household.

During the summer of 1921, Armstrong got involved in a local property case. There is some speculation that he was already in some financial difficulty, and if the decision went against him in this case he would be personally liable to pay back a deposit of £500 he had taken for the sale. During his trial, much was made by the defence of the fact that although Herbert had inherited his wife’s estate of several thousand pounds, he had not attempted to touch the money (suggesting that his money problems were not that bad). Regardless of how much or little debt he was in, Armstrong obviously decided that he could not pay the deposit back. Oswald Martin, another Hay on Wye solicitor, kept chasing him for the money and Armstrong kept evading him.


That’s how the pair came to be having tea on 26 October 1921 — Martin assumed the invitation had been extended so they could finally sort out this matter of the missing deposit. In fact, he said later, Armstrong seemed mostly interested in talking about local matters and even mentioned how he felt lonely after the death of his wife. She had been dead about eight months at this point, and there was as yet no suspicion associated with her passing.

In the end, it was the smallness of the town that really did for Armstrong, because when Martin was taken ill after that suspicious scone, it was the same doctor who had attended Katherine Armstrong who came to treat him. Dr Hincks immediately recognised Martin’s symptoms as similar. At the same time, Martin’s father in law, John Davies was having his own misgivings. He was a pharmacist, and had recently sold several packets of arsenic to Herbert Armstrong, supposedly so that the latter could kill the dandelions in his lawn. Knowing something about poisons, Davies put together this sale of poison with his son in law’s symptom’s after eating Armstrong’s food, and came to the conclusion that something nasty was going on. The three of them — Martin, Hincks and Davies — pooled their information and also realised that Mrs Martin’s sister in law had recently become ill after eating chocolates from a box delivered anonymously to their house a few weeks before. Upon inspection, these were found to have been tampered with, with a nozzle-sized hole in the bottom of each chocolate showing where another substance had been injected. The doctor sent some of Martin’s urine off for analysis, and when it tested positive for arsenic he alerted the Home Office as to his suspicions.

We’ll never know whether Herbert Armstrong was inspired by what happened to Harold Greenwood, or if it was just a coincidence that another solicitor in the same area was tried in a very similar case around the same time. We can be reasonably sure that he knew what had happened, though — local papers show that the tragedy of Mabel Greenwood’s and her husband’s subsequent marriage and trial were big news in Wales in the early 1920s. The authorities were also very aware of this case, and trying to avoid another high profile acquittal of a solicitor was a big reason why the police moved so slowly and cautiously in Armstrong’s case. Oswald Martin was advised by Scotland Yard not to accept any more invitations to tea or to eat any food sent anonymously to his houses, but it took several months for police to gather evidence.

In the meantime, Armstrong was passionately pursuing Martin, issuing regular invitations to have tea or dinner at his house. Martin couldn’t let Armstrong know what was going on behind the scenes, but he also couldn’t risk eating another poisoned scone, so he ended up making up farcical excuses as to why he couldn’t come round. Armstrong, meanwhile, became more and more pushy. The two solicitors had offices near to each other, and at one point Armstrong took to having his housekeeper from home come and set up tea in his office so that he could ring Martin and say ‘come round now! it’s all ready!’, thus putting his fellow lawyer on the spot. Martin managed to evade all of these traps, though, and Armstrong was eventually arrested on New Years Eve, 1921.


When the police took him, Armstrong actually had a packet of arsenic in his pocket, which looked particularly bad for him — almost as if he was making sure he was ready to poison someone at a moment’s notice. Dorothy L. Sayers borrowed this detail for her 1930 novel Strong Poison, which also deals with arsenic. Armstrong was a keen gardener and he stuck to his story throughout that he had been using arsenic to kill dandelions, but he didn’t have an adequate explanation as to why he separated his poison out into individual little packets that could be easily hidden in a suit pocket rather than just pouring it straight into the ground to kill the weeds. After he was arrested, the Home Office gave permission to exhume his wife, and pathologist Bernard Spilsbury was dispatched to Wales to collect evidence for a belated post mortem.

You might remember Spilsbury from a couple of previous episodes of the podcast. He was rather famous by the 1920s because of his evidence as an expert witness in the Crippen case in 1910 and the Brides in the bath murder trail in 1915. He was the one who opined on that bit of scar tissue purported to be from Cora Crippen, and who nearly drowned a volunteer lady swimmer by accident while trying to prove how a woman could be overpowered and drowned in her own bathwater. His involvement in the Armstrong case, therefore, helped to attract greater public attention to it.

Spilsbury found that Katherine Armstrong’s body was exceedingly well preserved, far better in fact than one would expect of a corpse that had been buried almost a year. He discovered a good deal of arsenic still present in the organs, and deduced that a major dose of the poison had been administered in the 24 hours before death. This contradicted Dr Hincks’s theory that Katherine had died of gastritis, and opened up the possibility that Oswald Martin was not Herbert Armstrong’s first victim. Since Martin had eventually recovered from the scone, it was with the murder of his wife that Herbert Armstrong was charged in January 1922.


Martin Edwards says in his excellent book The Golden Age of Murder that the novelist Anthony Berkeley “took a special delight in identifying with meek middle class professional men who found themselves driven to murder”. Berkeley, who was unhappily married and had extra marital affairs, seemed to identify with men like Crippen and Armstrong who had strong willed wives who didn’t survive very long. The newspapers of the time were full of gossip that Katherine Armstrong had only allowed her husband to smoke in one room of the house, and prevented him from drinking alcohol most of the time — clearly grounds for doing away with her. The whole idea of a husband being ‘henpecked’ and a wife ‘domineering’ seems extremely loaded and misogynistic to me, but that’s very much the lens through which this stuff was seen at the time.

Herbert Armstrong’s trial was very inspiring to Berkeley, who used it as the basis for his 1931 novel Malice Aforethought, published under the pseudonym Francis Iles. In this inverted mystery the reader is taken inside the mind of Dr Bickleigh, a mild mannered GP who poisons his wife in order to be with another woman. We see Bickleigh’s trial from his own perspective, knowing from the very first line of the book that he is guilty, yet somehow Berkeley makes the reader root for him to get away with it.

Herbert Armstrong maintained his innocence throughout, but he did not get away with it. Although the police didn’t actually have any evidence that he had administered the fatal dose of arsenic to his wife, his possession of a large quantity of the poison and the way in which her health had dramatically improved when she was away from him was enough for the jury to find him guilty. His appeal against the verdict was dismissed and he was executed at Gloucester prison on 31 May 1922, becoming the only solicitor in British history to be hanged for murder.

It’s fitting, I think, to give the last word on this much-fictionalised story to a fictional detective. As Peter Wimsey says in Unnatural Death: “Armstrong is supposed to have got away with many more crimes than he was tried for—it was being clumsy over Martin and the Chocolates that stirred up the hornets’ nest in the end.”

If Armstrong hadn’t tried to kill someone with a scone, his subtle, progressive poisoning of his wife would probably never have been discovered. Which makes you wonder: how many smarter murderers have managed to stop after their initial success and thus got away with their crimes? We’ll never know.


This episode of Shedunnit was written, narrated, and produced by me, Caroline Crampton. You can find show notes at where there will also be links to all the books and sources I mentioned. I provide transcripts for every episode of the podcast too: find them at

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I’ll be back on 29 April with another episode.

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