Born in Essex, Ursula Bloom was the daughter of the Reverend Harvey Bloom, of whom she wrote a biography entitled Parson Extraordinary, and she also wrote about her great-grandmother, Frances Graver (born 1809) who was of gypsy (Diddicoy) breeding. Graver became known as The Rose of Norfolk, (the title of the book by Ursula Bloom). Graver became the wife of the royal chaplain. She had eight children. Ursula Bloom lived for a number of years in Stratford-upon-Avon, which was the subject of her book, Rosemary for Stratford-upon-Avon
She wrote her first book at the age of seven. Charles Dickens was always a dominant influence; she had read every book of his before she was ten years of age, and then re-read them in her teens. A popular novelist, she wrote over twenty radio plays and non-fiction titles, and over 500 other titles. She appeared frequently on British television. Her journalistic experiences were written about in her book The Mightier Sword
Her hobbies included needlework, which she exhibited, and cooking.
Bloom married twice--in 1916 to Arthur Brownlow Denham-Cookes, with whom she had one son, Pip, born in 1917, and in 1925 to Charles Gower Robinson. Bloom became close friends later on in life with Dr Crippen's love, Ethel Le Neve.