Corbett v Corbett
The case of Corbett vs. Corbett of February 1970 set a legal precedent regarding the status of transsexuals in the United Kingdom.
It began as a divorce case at a time when the UK didn't regognise mutual consent as reason enough to dissolve a marriage, so Arthur Corbett sought a method of dissolving his marriage to the model April Ashley without the issue of inheritance rights.
His case was brought under the premise that, as Ms Ashley was born male (and should therefore be treated as male in perpetuity despite her change of sex) the marriage was illegal. At the time, medical opinion on transsexuality was divided and no consensus on whether Ms Ashley should be legally seen as male or female could be reached.
As a consequence, the judge (Lord Justice Ormrod, who was himself a medical man) created a medical 'test' and definition to determine the legal status of April Ashley and, by extension, all transsexual people. The result of this test (which defined Ms Ashley, a successful model, as a man) was then taken up and used to define the sex of transsexual people for many purposes until the introduction of the Gender Recognition Act 2004 (which ultimately defined the sex of transsexual people as whatever is on their birth certificate, until such point as a Gender Recognition Certificate corrects the birth certificate - hence for those who do not possess such a certificate, nothing has changed since 1970).
As a result of Justice Ormrod's decision, the unofficial correcting of birth certificates for transsexual and intersex people ceased - after all, their sex was now defined by case law and couldn't be argued with.