In a touching demonstration of father-son friendship, Prince William was spotted smiling brightly while his father, King Charles, made a lighthearted address at a state dinner for the Japanese Emperor and Empress who were in town.
Prince William seemed to take great note of the King's words, which touched on their mutual interests in fly fishing and Japanese pop culture. William couldn't help but laugh and give his father a funny look as Charles laughed about his poor fishing skills and his grandchildren's love of Pokemon.
The humorous exchange showed a more intimate side to the two royals and gave insight into their fun chemistry.
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The purpose of the state visit, which is the Emperor and Empress of Japan's first formal visit to the UK, is to foster diplomatic relations and honour the rich cultural legacies of both countries. The fact that the King was able to make his son smile indicates that the royal family is off to a wonderful start.
Emperor Naruhito and his wife begin a week-long visit to Britain on Saturday, visiting Oxford University, where they both studied, and attending a formal banquet with King Charles.
King Charles said: "I know from Your Majesty's fascinating record of your experiences at Oxford [University, UK]-as well as my memories of our time spent together at the opera and fly fishing-that these opportunities to spend time abroad create lifelong friendships and memories.
"I am only sorry to report that I haven't had any better luck with more recent attempts at fishing-the Pokemon phrase 'gotta catch 'em all' may resonate with my grandchildren, but for me, it is, perhaps, aspirational," the monarch added."
King Charles III hailed Britain and Japan's "close friendship" at a lavish state banquet for Emperor Naruhito and Empress Masako at Buckingham Palace on Tuesday as the Japanese royals began a three-day state visit.
It is the first state visit to the UK by a Japanese head of state since 1998, and, unusually for such a trip, it comes during a general election campaign.
Some typical political elements, such as a Downing Street visit, have been scrapped in line with neutrality rules, but all the traditional pomp and pageantry have been maintained.
The emperor and empress, who arrived on Saturday and held informal weekend engagements, were formally greeted by Charles and Queen Camilla in central London to the sound of gun salutes and the two countries' national anthems.