Born at Russell Square, London, England, she was the third of eight children of Favell Bourke Lee(1780—1841) and Barclays bank co-founder David Bevan (1774—1846). When she was six the family moved to Hale End, Walthamstow where her mother came under the strong evangelical influence of both the Rev. George Collison and the family governess Clara Claire. When Favell was twenty the family moved back to Upper Harley Street in London to enjoy a full social life and her father bought an estate in East Barnet which he named Belmont. There in 1831 Favell Lee Bevan became friends with Henry Manning, who was a friend of her brother Robert from their time at Harrow School. Manning was six years her junior and initially they shared an intense interest in religious questions. Any suggestion of a romance was brought to an end by her mother in May 1832 and Favell broke off their correspondence which was only re-opened in 1847 after the death of her father. Manning then wrote offering condolences and asking for the return of all his letters to her and offering hers in exchange. According to Audrey Gamble in her history of the Bevan family, his biographer regarded Favell Mortimer as one of the three most important women influencing Manning’s life.
In 1841, at the age of 39, she married the Reverend Thomas Mortimer, a popular preacher and minister of the Episcopal Chapel, Gray's Inn Lane, London. Thomas Mortimer was a widower with two young daughters, the elder of whom died young and the other suffered from severe depression necessitating long periods away from her family, much to Favell’s distress. He later became vicar of Broseley in Shropshire. Her niece and biographer painted the marriage as a happy one ending with his death in 1850. However, her nephew Edwyn Bevan commemorating the centenary of the publication of Peep of Day suggested that Thomas Mortimer had a violent temper and was sometimes cruel to her. Although the marriage was childless they adopted a young student for the ministry called Lethbridge Moore as their son in about 1848. He later became Vicar of Runton in Norfolk and after the death of her husband Mrs Mortimer moved first to Hendon and then to Norfolk where she cared for several charity orphans whom she saw educated and started in employment. She travelled extensively visiting friends and relations and eventually suffered from a series of strokes, becoming increasingly frail and dying at Runton with family and friends around her.
Before her marriage Favell Lee Bevan had overseen the religious education of children on her father's estates, at Fosbury, in Wiltshire and in East Barnet and her interest in educational writing grew from that experience. She developed her own method of teaching children to read based on an early kind of 'flash cards' rather than the traditional hornbook. Her teaching notes were collected and appeared as such works as Peep of Day and Reading Without Tears. According to Todd Pruzan, "For the better part of the 19th century, Mrs. Mortimer was something of a literary superstar to an impressionable audience, both in her native England and beyond." The Peep of Day series was immensely popular: over 500,000 copies of the original edition were issued; it went through numerous English editions; and it was published by the Religious Tract Society in thirty-seven different dialects and languages. Writing in The New Yorker on March 4, 1950, Mortimer's grandniece Rosalind Constable called the book, "one of the most outspokenly sadistic children's books ever written" referring to her great aunt's belief in the need to impress upon children the pains of hell that would result from wrong-doing and the rejection of salvation.
Like many women writers, her books initially appeared anonymously, as "By the Author of 'The Peep of Day.'" Her focus on introductions to other countries and cultures was perhaps ironic, given that she herself travelled outside of her native England only twice . She died at Runton near Cromer in Norfolk, and is buried in Upper Sheringham churchyard. Her way of simplifying religious ideas for very small children was criticised by some contemporaries, and to readers now her piety is unpalatable or amusing and her descriptions of other cultures are marred by unpleasant stereotypes; however, to the student of nineteenth-century children's literature, her texts are instructive.
