Streep’s portrayal of the state of dementia—the panic and the paranoia, the childishness followed by shaky reassertion of adulthood, the slippings and delusions—is exact, as is its scripting by Abi Morgan. In one powerful scene, desperate to drive the image of Denis from her head, she turns on every machine—telly, radio, blender, and so on—until the whole apartment roars. At first we might be puzzled why Denis’s presence is not a comfort to her, why she increasingly rails against it. Then we realize that the sanity she holds on to insists that he is dead, so if he is still appearing to her, it means she is going mad. “I will not go mad, I will not,” she insists at one point, a deliberate invocation of Lear.I wrote immediately after seeing the film that the use of Thatcher's dementia as a lens surprised me in how flattering it really was to Thatcher. Perhaps flattering is the wrong term entirely: one might prefer to say that it lends an emotive hand to its audience, meaning that regardless of one's views on Thacher's political career (Streep herself said, "The policies you can argue with, but...") you would almost certainly count yourself among a very small minority if you didn't feel strangely sorry for Streep's Thatcher. Maybe even concerned in a detached but familial, maternal way. The power of film, you see?
Filmmakers can't really play the Shakespearean game convincingly anymore, and there are very few artistic avenues that will allow you to do it intelligently. There are certain scenes — other audience members with whom I've spoken tend to complain — that underestimate the intelligence of the viewers, and that unnecessarily explain things that may have survived perfectly well without explanation. The King Lear allusion is made in such an 'up-front' way, it's easy to see where such people are coming from. We can make the connection ourselves. Thanks.
My original thoughts on the film here.