The wife of Thomas Hardy died of syphilis, according to research that unravels the mystery of why her husband was driven to expressing so much guilt in the elegies he wrote after her death.

Scholars knew that the author of classics such as Tess of the D'Urbervilles and Far from the Madding Crowd had an eye for pretty women and that Emma Lavinia Hardy had withdrawn affection from him, but they have long struggled to explain the guilt and self-accusation within his Poems of 1912–13.

Almost a century after her death, Robert Alan Frizzell, a retired GP, has come up with a retrospective diagnosis that provides an answer, revealing the terrible dark secret that had poisoned their marriage.

Publishing his research in the latest issue of The Times Literary Supplement, Dr Frizzell concludes that her irrational behaviour, inappropriate dress and “grandiose delusions” were among the debilitating symptoms of syphilis, which she had contracted from Hardy.

He said: “That was the cause of the hostilities between them in their last 20 years. They knew what she was suffering. Syphilis had the same sort of stigma as Aids today. If you caught it, straight away you would be stigmatised, in a way you wouldn’t have been for adultery.”

Dr Frizzell has no doubt that Hardy, along with his doctor and his wife, knew that she had fallen victim to syphilis when he wrote lines such as “Ah, that there should have come a change!/ O the doom by someone spoken” in The Change.

He began his research after reading a Hardy biography that said that Emma had died from gallstones. At her death in 1912, her husband’s doctor gave “heart failure and impacted gallstones” as the cause of death and commented, in a note to Hardy, that he thought she had suffered an internal perforation. Dr Frizzell said: “I thought, ‘it’s definitely not gallstones’. Purely on clinical grounds, I realised her last illness fitted syphilis.”

Forgetfulness, irritability, poor concentration and “grandiose delusions” are among symptoms of acquired syphilis, he said, along with inappropriate dress, personal appearance and behaviour.

Emma had suffered from delusions, Dr Frizzell said, even imagining that she was a greater writer than her husband, and that she had written one or more of his novels, when in fact she had acted as his amanuensis, merely taking down one of them from his dictation.

In their long, childless marriage, Emma is thought to have withdrawn all affection from her husband around 1891. Hardy lived on until 1928, marrying for a second time in 1914.

Dr Frizzell said: “He was luckier than Emma, as were approximately six out of ten of those who acquired syphilis in those pre-antibiotic days. The presumption must be that his own immune resistance to the spirochaete was of a different order from that of his wife.”

He added: “We know that Hardy had a weakness for pretty young women, and in the 19th century it was not necessary to be especially promiscuous to contract syphilis, just unlucky . . . But however unlucky he was to contract the disease, he was well aware that Emma, whom he must have infected in his turn, had by far the worst of it.”

Lilian Swindall, curator of the Hardy collection at Dorset County Museum, described the research as “very interesting and well-argued”, although she was surprised that Emma’s less than discreet maids would not have realised.

Claire Tomalin, the author of Thomas Hardy: The Time-Torn Man, said: “It’s absolutely fascinating, but I am sceptical of his arguments. It is impossible for anyone to know for certain whether posthumous diagnosis is right or wrong.”

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