It all started in unglamorous Watford, England, when Geraldine Estelle Halliwell, born in 1972 (sceptical industry journalists have moved the date back as far as 1962) to a Spanish mother and Swedish/English father, shed her parents’ Jehovah’s Witness values and began “jumping up on the [school] desks and singing.” Classmates remember that the gregarious teen “only wanted to have a laugh,” and that she was “really nice....