But where do you stop? Speaking as a Yorkshireman wasn't Richard III illegally usurped and everything that happened since invalid?
The point is such questions have to be settled according to the law.
This is where democracies and monarchies divurge. Contrary to popular belief a monarch was not free to change the law in any way he saw fit, he was as bound to it as the most modest farmer. Democracies on the other hand rewrite laws to suit the opinion of the majority - vox publica, vox Dei.
Laws of succession and property are complex, there is a sampling of some still in force here at Heraldica
No. Unless one holds to the hardline Jacobite position, Queen Elizabeth II is the only possible claimant to the British throne today, other lines having died out long ago.
There is a world of difference between a dispute over the succession, no matter how bloody, and the abolition of a monarchy. The former never questions the existence of fundamental laws and institutions, only the identity of the occupant of the throne. The latter, however, rejects all principles on which order had been based, decisively severing a country's link to its past and creating a new order contrary to the nation's heritage and traditions. No traditional conservative can approve of such a dismal development.