Only about 20% of male-to-female transgender people have had genital reconstruction surgery, and only about 5% of female-to-male, estimates Walter Bockting, a psychologist at the University of Minnesota medical school who has 20 years of clinical experience working with transgender patients.

BBC: Transgender Americans take on New York

Richard Beckett, a consultant clinical forensic psychologist, who has led research for the Home Office on adult male, adult female and adolescent females who engage in sexual harmful behaviour, is helping Taith with the research.

BBC: Sexually abusive girls rise prompts Barnardo's study