FYC: Pam Ferris in Children of Men

The film: A highly-praised dystopian action film set in 2027. It has much to say about our mortality, and is a stunning technical achievement -- more seemless, affecting battle scenes I have not seen. See Dargis for a graceful appreciation.
The actor: Heretofore unknown to me, save for her part as the aggressive battle axe Ms. Trunchbull in 1996's Matilda. Welsh by way of Kiwi. Also known for Aunt Marge in one of the Harry Potters and for her long career in British TV shows like "Rosemary & Thyme" and "Darling Buds of May."
The character: Miriam, a nurse-turned-rebel who can tangle with the best of 'em. Portly and dowdy: not your typical vision of an action heroine (save the dreadlocks), but she matches Clive Owen step for step. It's a true supporting performance. No flash, all texture. Cuaron could've cast a babe in this role, and the movie would've withered. Instead, we have this wonderful, mysterious, complete human being who quietly electrifies the movie's nervous system.
The moment: When she's describing her work on the frontline of extinction -- delivering humanity's last babies before our species goes inexplicably sterile. It could've been a theatrical monologue, but Ferris turns it into a profoundly understated bullet point on her war-torn resume. It makes her final scene all the more excruciating.

This post is part of StinkyLulu's Supporting Actress Blogathon. What actor would you nominate in the category? My runner-ups to Pam Ferris: Laura Harring and Pell James in The King and Diane Lane in Hollywoodland.