The Duke of Cambridge waas also ful of praise for the portrait.
Prince William said:: "It's beautiful, it's absolutely beautiful."
The Cambridges later attended a private breakfast reception at the London gallery to mark the unveiling.
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A fine and generally dry day with a light breeze and plenty of long sunny spells, though becoming cloudier through the afternoon.
Saturday will be the best day this weekend before rain on Sunday.
Clacton MP Douglas Carswell admits that he feared for his safety when he was mobbed group of anti-austerity protesters outside Westminster.