It's only a supporting role, but Shaw definitely makes his presence known. His charismatic and layered performance keeps the execution-happy King from being an out-and-out villain, instead making him a flawed and conflicted antagonist.
Most actors playing monarchs have it easy, in that they're playing figures from a past before film and television and have a greater degree of freedom in "creating" the character. Mirren had to balance her vision of the character against everything a contemporary audience already knows (or thinks it knows). Needless to say, she did it brilliantly.
"The grandmother of Europe," ruler for 63 years, Queen Victoria is a massively daunting historical figure. In Mrs. Brown, however, Dench makes her a very human and very accessible character. Playing that other Queen is what won Dench her Oscar, but it really should have been for this performance.
A character so nice, O'Toole played him twice. Well, "nice" might be pushing it. Still, there's no doubt that of all the great roles O'Toole has played, this is one of the very best. So great, in fact, that he received Oscar nominations for both films.
Actually, I'm not terribly fond of The Golden Age, but Blanchett's portrayal of the first Queen Elizabeth in Elizabeth remains a favourite of mine. The Queen has been played by many great actresses (including Helen Mirren and Judi Dench), but for me Blanchett's performance is the definitive one.