Under the 1701 Act of Settlement, this poses a thorny problem. As the law stands now, any future male sons born to William and Kate would take precedence in the line of succession over their (non-existent) first-born daughter. The House of Commons is already at work negotiating changes to the line of succession, which must eventually be approved by all 15 Commonwealth countries, a process that could take years.
The change can't come soon enough for The Telegraph's Cristina Odone, who notes the act is full of outdated and discriminatory provisions:
The present Act of Settlement is proof that the law, even an ancient law, is an ass; and not just because it favours male heirs. The Act bans Catholics, and even those who marry a Catholic, from the throne. Such discrimination invites 'vandalism'. Let the barbarians storm the gates, leaving in their wake the Act of Settlement in a heap of ashes; and let Queen Elizabeth III rule wisely for decades – with her beloved Catholic consort at her side.