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Can you provide me with a little information about Walter Winterbottom and his career as an England Team Manager?
Walter Winterbottom was England's first, youngest and longest serving England team manager. He is also the only England manager to have had no previous professional managerial experience.

Question: How long did he serve as an England team manager?
Self-contained rewrite: How long did Walter Winterbottom serve as an England team manager?