 Complete the following phrase:  The native line of kings came to an end in 1234; their heirs intermarried with French dynasties. However, the Navarrese kept most of their strong laws and institutions. The death of Queen Blanche I 1441 inaugurated a civil war period between the Beaumont and Agramont confederacies with the intervention of the Castilian-Aragonese House of Trastámara in Navarres internal affairs. 