Complex sentence: In this position, later in 1952, he famously made the announcement that British clinician Richard Doll had proved the link between smoking and lung cancer at a press conference throughout which he chain-smoked.
Split into simpler sentences: In this position, later in 1952, he famously made the announcement that British clinician Richard Doll had proved the link between smoking and lung cancer. He did so at a press conference, throughout which he chain-smoked.