 Tree supported Robert Donat in 1937's "Knight Without Armour" and played a young teacher in Donat's "Goodbye, Mr. Chips" in 1939.At the start of the wartime 1940s, he had four releases, "French Without Tears", "Return to Yesterday", "Just William" and "Major Barbara", but shortly after putting his promising film career on hold to aid the war effort, he lost his left hand in an explosion during service with S.O.E., while training French resistance fighters in the wilds of Scotland.The war came to an end during his extended recovery and, mindful of the effect of such an injury upon a performing career, he chose to retire from acting and pursue life as a gentleman farmer.