It's called male primogeniture, and it is an absolute contradiction of that basic principle of chivalrous behaviour of "ladies first".

BBC: Why the monarchy discriminates

The new legislation will end the system of male primogeniture, meaning male heirs will no longer take precedence over women in line to the throne.

BBC: Royal baby girl 'would be princess'

New legislation is due to go through Parliament that will end the system of male primogeniture that gave men precedence over women in line to the throne.

BBC: The Duke and Duchess of Cambridge

New legislation would end the principle of male primogeniture.

BBC: Wales

Under the rules of male primogeniture, ladies come last.

BBC: Why the monarchy discriminates

Professor Bob Morris, honorary senior research fellow at University College London's Constitution Unit, says it could actually be easier to abolish hereditary peers in the Lords than make changes to male primogeniture.

BBC: UK Politics

According to recent media reports, the Prince of Wales - while backing the end to male primogeniture (the principle that males take precedence in the royal succession) - has expressed concerns to officials about "unintended consequences" which could affect the monarch's role as Supreme Governor of the Church of England.

BBC: The Duke and Duchess of Cambridge