Complex sentence: At the beginning of 2004 Dean was left without a British Superbike ride after D&B Racing pulled out at the last minute and he was asked again to help Phase One retain the World Endurance Championship in which Dean had helped them win in 2003.
Split into simpler sentences: At the beginning of 2004 Dean was left without a British Superbike ride after D&B Racing pulled out at the last minute. He was asked to help Phase One retain the World Endurance Championship, which Dean had helped them win in 2003.