The June 2012 issue of History Today features an article, "The She-Wolves of Navarre," by Elena Woodacre which chronicles the lives of five queens of the kingdom of Navarre from 1274 to 1512.
Elena Woodacre writes:
Though not impossible, it was much more difficult for a woman in the Middle Ages to inherit the throne. Yet in a period when female succession was relatively rare the Pyrenean kingdom of Navarre, now a semi-autonomous region of Spain, had an impressive number of female sovereigns. Five women ruled the realm in their own right between 1274 and the annexation of the kingdom by Castile in 1512. How were so many women able to succeed to the throne?
The full article is available in the magazine.