Guy Lodge Film Critic It’s the stock answer that many a happy long-term couple has given prying friends and relatives to explain why they haven’t married: “We don’t need a piece of paper to prove our love.” True enough. What can official documents tell you of something as wily and elusive as human desire? Is a band of gold a safeguard against a change of heart? Of course not, yet millions want it anyway, a ratification of feelings that might otherwise seem slippery or intangible from the outside.