Unfortunately, Isabella was already engaged to Hugh of Lusignan, an important member of a key Poitou noble family and brother of Count Raoul of Eu, who possessed lands along the sensitive eastern Normandy border. Just as John stood to benefit strategically from marrying Isabella, so the marriage threatened the interests of the Lusignans, whose own lands currently provided the key route for royal goods and troops across Aquitaine. Rather than negotiating some form of compensation, John treated Hugh "with contempt"; this resulted in a Lusignan uprising that was promptly crushed by John, who also intervened to suppress Raoul in Normandy.
Hugh of Lusignan was an important member of what?
a key Poitou noble family