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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He co-wrote classic sitcoms including Dad's Army which was filmed in Thetford and Hi De Hi which was filmed in Dovercourt in Essex.
Rather cloudy day ahead with some patchy light rain in the south.
Weather looking rather unsettled over the next few days with patches of light rain forecast.