William's pregnant wife, Kate, is missing from the prince's arm - she cancelled her appearance at the premiere due to acute morning sickness.
McKellan, who plays the wizard Gandalf in the adaptation of J.R.R. Tolkien's work, told reporters Wednesday that it "feels proper" to celebrate the film in London, given that a large part of the cast is British and Tolkien was an English writer.
Blanchett, who plays elf queen Galadriel, said it was great to see so many fans turn out considering the cold weather was "enough to drive anyone away."
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