There has been some confusion over her birthplace. One national newspaper obituary records the Channel Islands; the borough of Leytonstone specifically records at Fairwood Court, Fairlop Road, London E11: "Fanny Craddock [sic] 1909-1994. On this site until 1930 stood a house called Apthorp, birthplace of the famous TV cookery expert Fanny Craddock [sic]; born Phyllis Pechey." Fanny's birthplace was named after Apthorp Villa, in Weston, Somerset, where her grandfather Charles Hancock was born.

Her birth was formally registered in the district of West Ham.

The first ten years of her life in London began with her living in destitution, selling cleaning products door to door. She then worked in a dressmaking shop. Things finally picked up for her when she began to work at various restaurants and was introduced to the works of Auguste Escoffier, which proved influential. She later wrote passionately about the change from service à la française to service à la russe and hailed Escoffier as a saviour of British cooking - although she also fiercely defended her opinion that there was no such thing as British cuisine: "Even the good old Yorkshire pudding comes from Burgundy."

Fanny married four times, twice bigamously. The first marriage, in 1926, was to an RAF pilot named Sidney A. Vernon Evans. The marriage was shortlived, as he died in an aeroplane crash a few months after the wedding. This left Fanny a pregnant widow. Within a year of giving birth to her son Peter, Fanny married again, in 1928, this time to Arthur W. Chapman. Another child, Christopher, was born in 1929, but when he was four months old, Fanny abandoned him and Arthur for a new life in Central London. In September 1939 she married Gregory Holden-Dye while she was still married to Arthur, but the new marriage lasted for only eight weeks. By that time she had met Johnnie Cradock, a major in the Royal Artillery who was already married, with four children. (It is believed that they met at a food exhibition, but this is uncertain.) He soon left his wife and family to be with Fanny. They were married in 1977, after the collapse of her television career, even though Fanny had never divorced her second husband, who was still living. She also shaved over ten years off her age on the marriage certificate.

In the early years of her life with Johnnie Cradock Fanny carved out a minor reputation as a novelist and children's author under the pseudonym "Frances Dale". As "Phyllis Cradock" she came to be regarded as an authority on the lost continent of Atlantis, which she connected with her lifelong belief in spiritualism. However, it was her first recipe book, The Practical Cook, that opened the door to Fleet Street in 1949. The Daily Telegraph already had a cookery expert, Claire Butler, so Fanny's first contributions were as "Elsa Frances", a fashion writer, and "Nan Sortain", a beauty consultant - as she later recalled, "all acne, leaking scalps and curious inquiries made on behalf of a mysterious 'friend'".

Evelyn Garrett, the woman's editor at The Daily Telegraph, asked Fanny whether she and Johnnie would like a few weekend breaks in the country "to find out if there is anything left that is worthwhile in the inns of England", and they soon began jointly writing a column. under the pen name of "Bon Viveur", which appeared in The Daily Telegraph from 1950 to 1955. This gentle experiment evolved into a five-year voyage of discovery, during which Fanny and Johnnie visited thousands of hotels and restaurants in England and abroad. The paper also provided Fanny and Johnnie with a basis for their "Kitchen Magic" extravaganzas, staged across the country, in which they turned theatres into temporary restaurants, as Fanny cooked vast dishes that were then served to the audience. They became known for roast turkey, complete with stuffed head, tail feathers and wings. Complete with French accents, their act was a presentation of drunken hen-pecked husband and domineering wife. At this time they were known as Major and Mrs Cradock. Their most prestigious event, when they filled the Royal Albert Hall for their International Christmas Cookery show in 1956, was dedicated to Escoffier.