Complex sentence: He had a memorable interview with Jeremy Paxman on the election night prior to the calling of his own seat and was stumped by the question of "Are we seeing the end of the Conservative Party as a credible force in British politics?".
Split into simpler sentences: He had a memorable interview with Jeremy Paxman on the election night prior to the calling of his own seat. Portilo was then stumped with the follow up question of "are we seeing the end of the Conservative Party as a credible force in British politics?".