To put Henry's desparate efforts to produce a legitimate son into their historical context, during his lifetime there was really only one good secure precedent for female rule. That was Isabella of Castile. Every other case of female rule that I have been able to find had involved civil war, rebellions or assassinations (or a combination thereof), or the woman being completely subordinate to a husband who ruled on her behalf. At the time of his death Mary Queen of Scots was barely four years old, and there was the awful current example of Juana la Loca in confinement at Tordesillas.
Ann