Marie Dobbs, who has died aged 91, was an author and continuator – a person who finishes the work of other writers; in the mid-1970s she completed Jane Austen’s final fragment of fiction, Sanditon.

The art of “continuation” came naturally to Marie Dobbs. She described herself as “the grasshopper type ... I take something up and fiddle and fiddle at it until I get it right. I suppose I’m what you’d call a finisher, though. I never give up half way. Even if I know a painting or a dress isn’t going to be very good, I go on until it’s done.”

In a varied life, her fiddling and finishing took her from Sydney, Australia, to Wells, Somerset, and found her dabble in journalism, gardening, painting, weaving and jewellery making. But she achieved her greatest success as a writer of fiction, first of short stories for women’s magazines, and then four novels, including Sanditon, which became a surprise bestseller and is currently being developed as a full-length feature film. Austen abandoned the novel in 1817 shortly before her death; Marie Dobbs published her “finished” version in 1975.

Marie Dobbs’s use of the pseudonym “Another Lady” for her completion of Sanditon – a reference to the fact that early Jane Austen novels were attributed to “A Lady” – sparked a literary guessing game over the identity of Austen’s co-author. Writing in the Financial Times, the novelist C P Snow said that “Another Lady” was “clearly an experienced writer with a sharp talent of her own.” Martin Amis expressed “surprise” at the ability of the “Other Lady” to “reproduce the tart periodicity” of Jane Austen’s sentences, concluding that she was obviously a “very professional writer – a rather more contemplative Barbara Cartland, one imagines.”

Philippa Toomey, in The Times, noted the challenge of emulating “the wit, the satirical eye, the delineation of character, the style, the extreme economy of technique, and the charm” of the Jane Austen canon. “Thanks and praise, therefore, to the Other Lady, for her tact, her taste, wit and discretion. She has provided us with a novel which ... dances and sparkles in sunshine and freshness.”

Marie Catton was born on June 20 1924 in Sydney where her father, Reginald, was a businessman. Marie graduated from the University of Sydney.

She left Australia in 1945, at the age of 21 – and did not return for more than half a century. “In order to obtain priority passage on a ship,” she later wrote, “I said that I had to go to England to take up the Winifred Holtby scholarship from Somerville College, Oxford. It was a scholarship available for Commonwealth students, but I had not won it. I just looked it up in the university handbook. Nobody checked.”

She was the sole Australian on board the cargo ship during the 10-week passage and had less than ten pounds in her pocket. Marie’s great-great-great grandmother, Mary Stevens, had made the same trip in the opposite direction 145 years previously, after being convicted at the Somerset Assizes and sentenced to seven years’ hard labour in Australia for stealing a roll of cloth worth 30 shillings.

Marie Dobbs arrived in England on Christmas Eve 1945. “The war was over, and I, who had little personal experience of it, still had all my reserves of adventurous dreams intact,” she recalled. “The people I met had been living in daily contact with war and were weary of adventure.” Having already worked as a journalist in Australia, Marie found a succession of temporary jobs in Fleet Street, working at one point for the spy-turned-editor Ian Fleming, who went on to write the James Bond novels. During a short stint with the Daily Express she was sent to Surrey to investigate complaints of new bed frames being used as fencing.

Tiring of the gloomy English weather, and her freezing bed-sitter off Baker Street, Marie left London for Athens in March 1946 to report on the Greek civil war. Over the next three years, she travelled widely in Greece and Turkey.

She moved to Moscow in 1947 after being offered a position as a librarian in the British embassy. There she found that Soviet restaurants offered a “bewildering variety of dishes,” all decreed in Moscow by some central planner, but most were permanently off the menu.

It was at the embassy that she met Joseph Dobbs, who during his time in Moscow held a variety of positions including press attaché, head of the Russian Secretariat section and Minister. The couple were married in 1949 and spent 13 years together in the Soviet Union under a succession of leaders, from Stalin to Brezhnev.

As the wife of the British embassy’s resident Kremlinologist, Marie became friends with a wide variety of Russians, from the writer Nadezhda Mandelstham to the cellist Mtislav Rostropovich. She also helped provide the West with some of the first insights into the Gulag prison system. She befriended the stranded Russian wives of British citizens who after marrying were banned by Stalin from leaving their country.

Marie drew on her Russian experiences for her first novel, Miss Bagshot Goes to Moscow (1960), which describes the comic adventures of an elderly English spinster who is mistakenly included in a visiting “peace delegation”. The manuscript was reviewed by the Foreign Office prior to publication, resulting in a request to Marie “to make your delegation less true to life” for fear that it might offend the Labour politician Barbara Castle.

As a short-story writer, Marie Dobbs had used the nom de plume Alison Walpole, a combination of the daughter she never had and the street in Chelsea where she and Joe purchased their first house. At the Foreign Office’s request, she disguised her identity even further by changing her pen-name to Anne Telscombe, after a village in Sussex where her family spent the idyllic, sun-blessed summer of 1959.

She published two further novels – Miss Bagshot goes to Tibet (1962) and The Listener (1968) – under the same pseudonym.

Marie Dobbs interests were wide ranging, incorporating both highbrow and lowbrow culture. She loved Austen’s Emma but also Strictly Come Dancing and Dame Edna Everage.

During the last weeks of her life she regaled visitors to her hospital bed in Taunton with stories – delivered with a sharp sense of humour and astounding memory for detail – of her travels around the world. She had accompanied her husband on diplomatic postings to India, Italy, Poland and the former Yugoslavia.

Eventually settling in Somerset, Marie remained fiercely proud of her Australian roots. She refused to either give up her Australian citizenship or acquire British nationality. Shortly before her death a nurse asked her to name her favourite place. Without hesitation, she replied: “Australia”.

Her husband predeceased her and she is survived by their four sons. For all her success as a writer, Marie Dobbs once said that “the biggest and most demanding thing I have done in my life is to bring up a family of four boys.”