In 1939, Winn was the first British war correspondent to cross the Maginot Line. He served as a Royal Navy able seaman, during the Second World War, training at HMS Ganges and becoming a CW (Commission Candidate Wartime) before injury led to his medical discharge. His book 'Home From Sea' published in 1943 recounts his life in the Royal Navy. Another book, PQ17, was an account of his experiences, as a journalist, on Convoy PQ 17 during the Second World War. After the war, he wrote numerous books and magazine articles, and appeared on radio and television as well as in films. He frequently compered the BBC Radio show "Housewives' Choice", with David Jacobs, from the early 1950s to the mid 1960s. He was a friend of W. Somerset Maugham and it is said that the character George Potter in Maugham's 1941 book "Strictly Personal" was based on him.