Margaret Moncrieff was a distinguished cellist whose performing career took her across the British Isles and to the wider world. She was also a fine teacher at the Royal College of Music, the Royal Northern College of Music and Wells Cathedral School. In her sixties, under the pseudonym Helen McClelland, she also developed a second career as a children’s writer and biographer.

Helen Margaret Moncrieff was born in 1921 into — as she recalled in her autobiography, Worlds Apart (2003) — the regimented environment of the Edinburgh legal aristocracy. Her father, Alexander Lord Moncrieff, ended his life as Lord Justice Clerk of Scotland and a Privy Counsellor. Yet the Moncrieffs, whose founding father had come from Spain in the 12th century and who had intermarried with Huguenots in the 18th, were cultivated eccentrics.

Her father published poetry as well as legal writings and was an honorary Fellow of the Royal Society of Edinburgh. A cousin, Hope Mirrlees, was a friend of T. S. Eliot and the “ghostly daughter” of Jane Harrison. Margaret’s mother, Helen Adams, had studied German literature at Bedford College in the 1890s. Margaret inherited their capacity to live against the grain. A stint at St Mary’s Convent, Ascot, when she was in her teens nearly ended in expulsion when she organised first a duel in the chapel with pins and then an unsanctioned trip to the races.

Both parents encouraged Margaret’s musical promise from her early years. As a child, she was sent to the private music school run by Ruth Waddell in Edinburgh. Later her parents, while insisting she should take a music degree at the University of Edinburgh (which she considered a waste of time), also paid for her to study the cello with Pierre Fournier in Paris, where she lived for most of two years.

The experience in Paris was to influence not just her musical development but also her attitudes to life. She returned with fluent French and a lifelong attachment to foods then considered extraordinary in the British kitchen, such as yoghurt and garlic.

As a player, Moncrieff specialised in chamber music. In search of a pianist in the mid-1950s she met Alexander Kelly, whom she married in 1957. The two, as a duo and in combination with musical friends such as the flautist William Bennett and the cellist Christopher Bunting, made many concert and broadcast appearances.

A liking for unusual repertoire was encouraged by the series The Innocent Ear on the BBC Third Programme; later she regularly performed works such as the Cello Sonata No 1 by Jean Huré. She also performed works by composers such as Hans Gal and Peter Wishart, who became close friends.

Strikingly beautiful, Moncrieff was not a flamboyant player but impressed by her deep musical intelligence and understanding of a composer’s emotional world — qualities she would pass on to her many pupils.

Her writing was at first separate from her music: it was not until 2001 that she published a novel, Time and Again, under her own name. As Helen McClelland, she was best known for her biography of the school story writer, Elinor M. Brent-Dyer, an astute and elegantly written study based on extensive research in Austria and Switzerland, the locations of the fictional Chalet School, as well as in South Shields and Hereford, where Brent-Dyer had lived. While writing of and around Brent-Dyer with sympathy, she was herself a subtler and more inventive writer, as reviewers commented when she published her pastiche novel, Visitors for the Chalet School (1995). In it the aggressively genteel Lady Davidson snubs a shy friend of her daughter’s who committed the terrible faux pas of being first to extend her hand when introduced. This masterpiece of comic observation came from deep conviction. Moncrieff detested snobbery and pretension. Not “charming” in a superficial sense — she could be formidable at times — she was loved by a huge circle including students and friends from around the world.

A life in which she had gone from childhood holidays on an uncle’s yacht to camping out with her husband and children in a remote West of Ireland cottage without electricity or running water inspired a humorous conviction of the superiority of the present. To the end of her last illness, she retained her lucidity, her curiosity, and her joy in life.

Her husband predeceased her in 1996. She is survived by her two daughters, Catriona Kelly, Professor of Russian at the University of Oxford, and Alison Moncrieff-Kelly, also a cellist.

Margaret Moncrieff, musician and writer, professor at the Royal College of Music, was born on February 6, 1921. She died on November 12, 2008, aged 87