Complex sentence: As a historian, writer and broadcaster his work has reflected on the relationships that he had with Pablo Picasso, Braque, Leger and his longtime companion, the acerbic English art critic and Cubism expert, Douglas Cooper.
Split into simpler sentences: As a historian, writer and broadcaster, his work is connected to his personal acquaintance with many leading 20th century artists, among them Pablo Picasso, Braque and Leger. His longtime companion was the acerbic English art critic and Cubism expert, Douglas Cooper.