What is at stake in the Supreme Court gender case?

There are two broad sides to the case.

For Women Scotland, who say sex is an immutable biological fact; and the Scottish government, who say it can be changed with a gender recognition certificate.

Trans people see this case as challenging their very identity and fear that if the ruling goes to For Women Scotland, it would undermine their rights in their acquired gender.

They would still be entitled to protections under the Equality Act’s characteristic of “gender reassignment”, but not against discrimination on the grounds of sex.

So the ruling could determine whether a trans person would be able to pursue, for example, an equal pay claim as a woman.

For all the talk of the definition of “woman”, there was also a lot of focus on female-to-male transitioners – and in fairness there are just as many of them as there are male-to-female, according to census data.

Both sides in court seemed to agree that someone registered female at birth, who acquired a gender recognition certificate as a man, would lose their sex-based rights and access to spaces reserved for women.

While the government said this was in line with their choice, Aidan O’Neill – the KC representing For Women Scotland – argued that it amounted to protections being stripped from natal women, which he said was to “capitulate to the patriarchy”.

There was also a lot of focus on the idea of a “pregnant man” – the possibility of someone who gets a gender recognition certificate stating they are a man nonetheless becoming pregnant.

Would they still be entitled to pregnancy and maternity benefits enshrined in equalities law? Could they insist on being registered as the “father” of the child?

This is an extremely niche example which might ultimately only affect one person in tens of millions, at the most. Mr O’Neill had to produce case law which was “unfortunately only in French”.

But the judges in London may still have to come up with an answer to the question.