From 1060 to 1067 Baldwin was the co-regent with Anne of Kiev for his nephew Philip I of France, indicating the importance he had acquired in international politics. As count of Flanders, Baldwin supported the king of France in most affairs, but he was also father-in-law to Duke William II of Normandy, who had married his daughter Matilda. Flanders played a pivotal role in Edward the Confessor's foreign policy when the king of England was struggling to find an heir. Historians have argued that he may have sent Harold Godwinsson to negotiate the return of Edward the Exile from Hungary, and passed through Flanders, on his way to Germany. Baldwin's half-sister had married Earl Godwin's third son, Tostig. The half-Viking Godwinsons had spent their exile in Dublin, at a time William of Normandy was fiercely defending his duchy. It is unlikely however that Baldwin intervened to prevent the duke's invasion plans of England, after the count had lost the conquered province of Ponthieu. Baldwin died 1 September 1067.