Kate Saunders, who has died aged 62, was a prize-winning novelist, journalist and critic whose many achievements emerged despite a life of suffering and loss.

Kate initially worked as an actor, joining the National Theatre in 1983, an experience that inspired her second novel, Storm in the Citadel (1989), and the third of her detective novels, The Mystery of the Sorrowful Maiden (2021). She also made an early appearance as a policewoman dated by Rodney Trotter in an episode of Only Fools and Horses in 1982. Being steeped in Victorian and Edwardian classic literature from childhood, however, she soon realised that her true calling was writing, and by the age of 26 had won a Betty Trask prize with her first novel, The Prodigal Father (1986). As she put it, characteristically: “I was quite plain for an actress, but for a writer I was GORGEOUS.”

It was the start of a career that produced more than 20 novels for adults and children, ranging in genre from historical romance to detective stories to children’s books. A columnist for the Sunday Times, the Daily Telegraph, the Sunday Express, She and Cosmopolitan, she judged the 1990 Booker prize, and persuaded her fellow judges to choose AS Byatt’s Possession as the winner. She also judged the 2007 Women’s prize in the year that it was won by Chimamanda Ngozi Adichie’s Half of a Yellow Sun.

The eldest daughter of six children, Kate was born in London, into a devout Anglo-Catholic family of bohemian charm, warmth and eccentricity. Her father, Basil Saunders, was an early public relations advocate and her mother, Betty (nee Smith), was a reporter on the Church Times. Their house in Dartmouth Park Avenue was so chaotic that Kate remarked that “had we not been middle-class, we would probably have been taken into care”. She and her siblings all eschewed university for careers, mostly in journalism or publishing. Kate was educated at Camden school for girls, and trained with the Anna Scher theatre group.

She became a regular and glamorous contributor to radio and television, with appearances on BBC Radio 4 programmes such as Woman’s Hour, Start the Week and Kaleidoscope and, in 1990, as a guest on the first episode of the long-running TV news quiz programme Have I Got News for You. Tall, blond, strikingly attractive, full of salty wit and self-confidence, she was often to be seen in the Groucho Club and helped found the Orange (now Women’s) prize for fiction. This all changed when she gave birth in 1993 to her only child, Felix, and learned on the same day that she had multiple sclerosis.

The news was kept secret from all but her immediate family, but she signed up to write five historical romances, starting with her epic, Night Shall Overtake Us (1993), about a group of young idealists growing up during the first world war. It was a bestseller, but equally good was one of her wittiest romantic comedies, Bachelor Boys (2004), about two contemporary north London brothers who abandon their professions to pursue work in the arts for which they have minimal talent.

However, it was her children’s series, The Belfry Witches, which began with A Spell of Witches (1999), that initially made her name. Based in part on her own sisters, it featured two mischievous witches and their cats, and was made into a BBC television series.

She also co-wrote Catholics and Sex (1992) with Peter Stanford, then editor of the Catholic Herald, and they later presented a television series based on the book on Channel 4.

A passionately devoted mother, she was the breadwinner in her small family. Her husband, Philip Wells, whom she married in 1985, had briefly worked in the City but gave this up to attempt to write fiction himself. The marriage foundered, and Kate was left with a young child and, following her divorce, no savings. In 1999, she moved back into the family home in Dartmouth Park, sharing it with her eldest brother, Bill, and sister Charlotte. Eventually, this too was sold, and the three siblings plus Felix moved to Archway, which was to be her final home.

Increasingly frail, she kept writing, producing several children’s books, including magical comedies such as Beswitched (2010), Magicalamity (2011) and The Whizz Pop Chocolate Shop (2012). An ardent fan of CS Lewis’s Narnia books and E Nesbit, she found increasing success and comfort in what she termed “the prelapsarian” world of child readers. She was also a contributor to the 2016 authorised Winnie-the-Pooh sequel, The Best Bear in All the World.

However, as a teenager Felix became increasingly depressed, and took his own life aged 19. The shock and grief of this brought on the deterioration of Kate’s MS, which went from relapsing-remitting to advancing, and could no longer be kept secret. It was now that she wrote her masterpiece, Five Children on the Western Front, published by Faber in 2014, and, as she put it, “the book of my life”.

She remembered a scene from the third book in E Nesbit’s Five Children and It trilogy, The Story of the Amulet, in which the Psammead (the wish-granting sand-fairy) allows the five children to visit their friend the Professor in the future. “I was obsessed with this scene … ” she said in an interview. “These little children come back to visit, and he knows what has happened to them. Of course, they leave him crying. I thought, ‘this is the moment where we come in’.”

She had worked out that the five children of E Nesbit’s Edwardian classic of 1902 would, just a few years after their magical adventures, have lived through the first world war. The mix of wit, comedy and tragedy won her the 2014 Costa children’s book award, and was shortlisted for the Guardian and Carnegie prizes for children’s literature. Her novel The Land of Neverendings, about a child’s journey through a land of toys following the death of a sibling, was also shortlisted for the 2019 Carnegie medal.

Besides her children’s books, Kate also published a detective series about a Victorian archdeacon’s widow, Mrs Rodd, starting in 2016 with The Secrets of Wishtide. With gentle humour and details of how an impoverished clerical widow survives in her Hampstead cottage with “a tiny wink of fire”, it married her love of Dickens and Trollope to ingenious murder mysteries. Her last children’s book, A Drop of Golden Sun, about a family of child actors, will be published by Faber in 2024.

Kate’s friendship, kindness, courage and wit illuminated many lives. Conversations with her would encompass everything from feminism and literary fiction to leftwing politics, always punctuated by robust laughter.

An astute critic who still reviewed for the Times and the Jewish Chronicle, she was unstinting in her support for authors she esteemed, and never bitter at her fate. She became increasingly dependent on her youngest sister, Charlotte, who looked after all practical needs so that Kate could continue to produce a book every two years. One of my last memories of her was discussing Jane Austen’s Mrs Smith, Anne Elliot’s disabled and impoverished friend in Persuasion, whom she closely resembled.

Sipping champagne at home with her friends after receiving the last rites, she died as she had lived, with courage, grace and style.

She is survived by her siblings Etta, Louisa, Ed and Charlotte.

• Kate (Katharine Mary) Saunders, writer and actor, born 4 May 1960; died 21 April 2023