Complex sentence: Duveen eventually became "the art dealer", through shrewed planning and through his insight into human behaviour if a great painting came into the market he had to have it, no matter what, he always out did his bidders and eventually acquired the best collections.
Split into simpler sentences: Duveen eventually became "the art dealer", through shrewed planning and through his insight into human behaviour. If a great painting came into the market he had to have it, no matter what, he always out did his bidders and eventually acquired the best collections.