John Gielgud did not receive an Oscar nomination for portraying Cassius in Julius Caesar.
The brilliance of Gielgud's performance though is that he portrays
Cassius's urging toward Brutus to be quite false, and merely Cassius
manipulating Brutus. This is never spoken of by Cassius himself but
rather shown wholly by Gielgud's work. Gielgud is fantastic in the
moments where frankly Brutus is simply not looking at Cassius and
Gielgud uses these moments to portray the true nature of Cassius's
intent. Gielgud silent reactions when Cassius is left to his own
thoughts does not portray Cassius as a man who is trying to save Rome
from a man who has become a tyrant. No Gielgud instead portrays a
searing malice in Cassius as he looks upon Caesar and speaks the words
against him. Although in words and even in his delivery Gielgud has
Cassius claim a conflict of sorts Gielgud shows nothing but a distinct
hate in Cassius's eyes. Gielgud is striking as he creates this sinister
duplicity in the character being convincing as he persuades Brutus while
still conveying the real motivation in Cassius.
Gielgud is excellent in the way he plays with this act as the film goes on, never fully dropping it, although obviously relinquishing it somewhat when the men do kill Caesar. Where Mason presents Brutus clearly feeling guilt even as he performs the coup de grâce and tries to uphold the righteousness of the actions Gielgud does not hold to the same pretensions with Cassius. With Brutus dead and the man thinking of their actions Gielgud brings a smile to Cassius face as he ponders about how the future will see this deed. Gielgud presents Cassius as loving having killed a man he hated, there is no guilt whatsoever, only a certain joy as perhaps he sees his own chance for power soon to come. Gielgud keeps the act going though when Caesar's loyal man Mark Antony (Marlon Brando) comes on the scene. Gielgud changes Cassius from the man lusting after power to now a somber sadness fitting of a sensible and honorable man who surely killed Caesar only for the goodness of Rome.
After the overthrow goes much more roughly than expected Gielgud reveals all there is to Cassius when Brutus calls him on his obvious personal corruption. Gielgud is great as he reduces Cassius to almost nothing as he simply sneers angrily at actually being seen for what he is rather than what he pretends to be. This can only be momentary though as they do have a war to fight which Brutus still believes in even if the odds seem against them. Gielgud is quite moving as he seems to make Cassius create a false image again although this time it is not to convince Brutus but rather himself. Brutus still speaks for the good of Rome and Cassius seems to go along with it. Gielgud brings the brave face to Cassius as he tries to stand tall with Brutus yet Gielgud once again brings an undercurrent of something else. This time though it is a dread and a fear as Gielgud shows that in his heart Cassius knows that they are doomed. Gielgud is terrific as through the final moments of Cassius he tears away the false hopes of the man to reveal a man whose seen all his plans go up in flames. John Gielgud on his own gives a great portrait of betrayal and deceit but it works especially well against Mason's portrayal of honesty and devotion.