Complex sentence: Progressively minded and looking for a vehicle to address what he saw as the problems of society, he attended the Liberal Party's 1960 conference in Kingston which was held while the party was in opposition to explore new ideas the party should embrace.
Split into simpler sentences: Progressively minded and looking for a vehicle to address what he saw as the problems of society, he attended the Liberal Party's 1960 conference in Kingston. This conference was held while the party was in opposition to explore new ideas the party should embrace.