The prosecution of Charlotte Hough in the early 1980s was one of those rare court cases which not only feature in the daily news and become the object of everyday gossip but also, even while the case was still current, warrant fervent discussion in Parliament.

Hough (pronounced “how”) seemed an unlikely candidate for the role either of victim or of murderess; in fact she was an unlikely participant in the world of justice, criminality and the publicity that goes with them all. But above all she was an example of the suffering that a woman of her character and background — naive, innocent, just over 60 years old, pleasantly eccentric and what might be called a recognisable member of the chattering classes, the Hampstead intellectuals — would endure in prison.

Her reluctance to write about the experience afterwards, though urged by her friends to do so openly, meant that the horrors she endured are by now lost to any social historians who might be interested.

In the House of Lords she was described in glowing terms; her goodness, her talents, her Christianity — all were emphasised. She was so unlikely to be involved in such a case that when the police came to arrest her she was in the middle of breakfast and took it for granted that she could finish it and visit the police station in half an hour. It was the first of a series of shocks, to be told that she could not finish it but must come at once. The police, she kept emphasising, were “very nice”, but she was held for 12 hours and questioned almost hourly.

To the author of about 30 children’s books and a single adult one, ironically a detective story, and the illustrator of many more, the language to which she was subjected and in which she had to answer seemed foreign.

Gentle and a good listener, she must have replied in her usual manner, ingenuously unable to follow quite what had happened, who had been to the police about her and why she was being suspected of murder. No doubt she told the whole truth as she knew it, unable to see what she had done wrong or what the outcome would be: naive, perhaps, but never devious. Eventually she was given nine months in prison for attempted murder, and she served six of them. It had been a case of jumbled good intentions, of kindness that proved legally askew and of friendship taken too far.

She was born Charlotte Woodyadd in Brockenhurst, Hampshire, in 1924, to a father aged 50 and a much younger, very attractive mother whose first husband was killed in the war, leaving her with a son. Charlotte had an unusual background. Her father was the local doctor, her mother became an actress, singer and pianist, and brought the child up on her own, the father refusing to contribute.

On her father’s side the family (which she later had researched for a grandson) went back to the Conqueror; on her mother’s, it came from Lancashire. (In prison, when she was asked where she came from, the first question put by other prisoners, she was never believed when she said Lancashire because she had no accent from there.) She went to the rather progressive school Frensham Heights, where the poet and folk-singer Sydney Carter, whom she remembered affectionately, was on the staff.

Leaving early, she went into the WRNS, since in her day it was thought unpatriotic, she said, to consider university as opposed to one of the Services. She married early; her husband Richard Hough (later a well-known biographer whose subjects included Mountbatten; obituary October 8, 1999) was in the RAF, and they were married in uniform.

There were five children of the marriage, one still-born (and, eventually, eight grandchildren). Neither she nor her husband had had any professional qualifications, and their early married years were a struggle. One thing Charlotte could do was drawing. Hawking her sketches around to publishers, she managed to find work as an illustrator of children’s books (she was especially good at drawing children and horses, something oddly rare among illustrators), and later wrote children’s books of her own, illustrated by herself. The first, Tiger Jim, was accepted by Faber, and after that it was fairly plain sailing: she published about 30 light, short tales with attractive scribbly drawings, all taken by leading firms — Faber took 11 of them; others were published by Hamish Hamilton, Heinemann, Puffin and Dent.

Finally she wrote an adult book, The Bassington Murder (1980) — a few years later the title featured large in accounts of her trial in the newspapers, which liked the idea of a detective story writer being herself accused of murder.

Her marriage ended in an unhappy divorce and, after several voluntary jobs, Hough became a Samaritan in Kent, where she had a holiday cottage. It was a demanding commitment, and she was given four old women to visit regularly. She became fond of them all, particularly one, Annetta Harding,who, seriously arthritic and nearly blind, told her she intended to take her own life when things got too much for her. Hough offered to be with her, if she wanted it, when she took the lethal pills she had collected. Harding was touchingly grateful, and Hough sat with her for several hours until she took the pills. The house in which Harding lived was locked at 10pm, and she begged Hough to leave in good time to avoid being involved in her death. But when she came to go, Hough realised that Harding, although in a coma, was still breathing. Several plastic bags which Harding had intended to put over her head if necessary were placed beside her chair, so Hough did what she knew Harding had meant to do. Almost at once she stopped breathing. Hough removed the bag and left.

She had acted out of affection for and loyalty to her friend, and nothing, presumably, would have happened if she had not (incredibly, it seemed afterwards) told a Samaritan friend with whom she had worked closely, swearing her to secrecy. The woman went straight to the director of the Samaritan branch, who went to the police. The first Hough knew of the affair was when it appeared on the front page of the Daily Mail.

The law ground on, Hough was tried and avoided conviction for murder. She was sent to an open prison, an easier option than others, for nine months for attempted murder. She served six months.

Much of her ordeal in prison was a result of the English class system, the fact that there was no one among inmates or staff who had or wanted to have any social or educational link with her. On arrival she had a terrifying experience, being threatened with face-slashing or even death. Part of it was connected with her offence (plastic bags were left prominently about), but virulent class hatred was also obvious. Gradually she overcame it by becoming just another inmate, part of the landscape; newcomers, unable to place her, sometimes addressed her as “Miss”. The food was poor and the prisoners were malnourished, but six months inside was not too long to affect her health, and chocolate, which could be bought, had good psychological as well as physical effects. Gardening became her favourite activity.

Lord Longford, who had championed Hough outside, visited her twice, opening his arms wide to hug her when they first met. And at the prison door, when she left, was a car full of her family, including her daughter, the novelist Deborah Moggach. Inevitably her thoughts turned to the women who left prison with no one waiting at the door and no supportive family and friends to go to. No wonder she was a member of the writers’ organisation PEN, which campaigns for prisoners abroad in much worse conditions than hers had been.

Charlotte Hough published nothing more. In 1997 she married Dr Louis Ackroyd, a widower formerly in the Colonial Engineering Service and Nottingham University. He predeceased her, and she is survived by her three daughters.

Charlotte Hough, writer and illustrator, was born on May 24, 1924. She died on December 31, 2008, aged 84