“Heralding an end to more than 300 years of English constitutional tradition, the Prime Minister will urge Commonwealth leaders to end laws that pass the Crown to the oldest male heir. Under the current rules of primogeniture, any male child takes precedence in the order of succession over his sisters. That would mean that any son born to Prince William would become King even if he had an older sister.”
Daily Telegraph, 28th October 2011
Source: www.telegraph.co.uk