B. M. Gill was born Barbara Margaret Gill on February 15, 1921, the daughter of an Irish sea captain and his Welsh wife. Gill began writing at the age of eight, after her father encouraged the imaginative child to set down her stories about secret passages and mysterious doings. In accordance with her mixed parentage, the young Gill was educated at a convent school but attended a Presbyterian church on Sundays. This contradictory religious upbringing is reflected in Nursery Crimes, Gill’s most comical, most chilling, and best-written novel.
After leaving school at the age of fifteen, Gill worked in the Trinity House Office in Holyhead, “learning about buoys, lighthouses and Elder Brethren.” She worked there until her marriage at the age of twenty-one to a Mr. Trimble, whom she has not fully named or discussed in interviews. The marriage soon ended in divorce, leaving Barbara Margaret Trimble with a young son, Roger, to support. Casting about for a profession that would allow her to work at home, Gill trained as a chiropodist and set up a private practice for four years. She then retrained as a nursery school teacher and taught for fourteen years in a village school in Somerset.
While teaching, Gill began writing radio scripts and short stories for Chambers Journal and John O’London, two literary magazines. Using the pseudonym Margaret Blake, she also began writing romantic suspense novels that were serialized in Woman and Woman’s Own. Encouraged by the steady sale of her writing, Gill quit her teaching job, only to discover that because of rapid inflation she could not support herself by writing alone. She therefore returned to chiropody and worked in a public health clinic for six more years before retiring.
On retirement, Gill returned to her mother’s native Anglesby in Wales, resumed her maiden name, and began writing detective stories. Her first novel, Target Westminster (1977), deals with a plot to blow up the House of Parliament. Her second book, Death Drop, revolves around a grieving father’s attempt to discover the truth about his son’s “accidental” death at a school outing; this work was reprinted in the United States and was nominated for an Edgar Allan Poe Award. Gill’s postretirement career as a mystery writer was well on its way. Her fourth book, The Twelfth Juror, won Great Britain’s top crime award, the Gold Dagger, as well as a second Edgar nomination in the United States.