Although it joins Eyes Wide Shut and Die Hard in the “I guess it’s a Christmas movie” pantheon, Pablo Larraín’s biographical psychological drama Spencer (A-), about the Yuletide weekend in which Princess Diana chooses to split from the royal family, is a melancholy masterpiece. Kristen Stewart is luminous in the lead role, brilliantly humanizing a public figure we think we all know and plumbing the depths of her spiral into despondency. Larraín’s frenzied fever dream frames its troubled protagonist with such a splendid mise-en-scène of mounting formal and claustrophobic environments, a viewer could well believe it’s a slo-mo horror film as much as a tragedy. The film is often quietly observant, which makes the moments of rage and revelations pulse all the more. For every nightmarish sequence around the corners of her lonely world, there are also tender moments depicting the fun and games Diana furtively plays with her sons. Several supporting performers stand out: Timothy Spall is a hoot as Equerry Major Alistair Gregory, with a constant puss on his face as he tries to reign in our heroine to do her duty, and Sally Hawkins is a delight in a small role as a confidante and royal dresser who whispers into her wanderlust. Deck these halls with Oscars already!