Prince William made a comment worthy of his gaffe-prone grandfather as he visited Japan House in London on Thursday.
The Duke of Cambridge, 34, asked a group of schoolchildren whether they had tried "much Chinese food" as they practised picking up edamame with chopsticks at the new centre celebrating Japanese culture.
He quickly corrected himself, adding: "Um, Japanese food. Have you had much Japanese food? No? Not too much. Do you like sushi? It's delicious, it really is yummy."
The London site is the newest opening for Japan House, with outposts already in Los Angeles and Sao Paulo.
The centre, which houses a restaurant, shop and library as well as exhibition and workshop spaces, aims to create a greater understanding of Japan among the British public and to deepen cultural, social and economic bonds between the two nations.
William, who visited Japan in 2015, was joined at the opening by Japan's Deputy Prime Minister Taro Aso.
Brief and uncharacteristic slip-up aside, William was the perfect royal ambassador throughout the visit - even gamely sipping a celebratory cup of sake at 11am.
The second in line to the throne arrived by car from Kensington Palace, just 200 yards away.
Asked why he hadn't walked, an official said it was for "security reasons" and his presence certainly drew a large crowd with camera phones around the store.
The prince viewed some of the exquisite goods on sale and walked around an exhibition of metal craftsmanship, watching the ancient craft of copper-beating in action.
Along the way he met Haruna Yamada and Hirokazu Kobayashi, the exhibition designers, who told him they had met at university. "Like myself and my wife!" he exclaimed. "My wife is the artistic one of the couple, not me, unfortunately."
Upstairs he met leading Japanese chef Akira, who has set up an eponymous restaurant in the store, and showed him a beautifully presented Bento Box containing everything from tuna and sea urchin in a truffle cream sauce to shitake mushroom tempura.
"Very impressive," William told him, as he helped himself to a salmon sashimi. "Thank you very much. My wife and I love sushi. We might have to come down here for lunch when no-one else is in.
"You must get a lot of Japanese visitors here. So do lots of people come in and ask for a burger? That's what usually happens, doesn't it?"
He then sat with a group of local primary school children who were learning to use chopsticks and origami skills.
As the prince sat down at the table one of the children told him flatly that he was tired. Laughingly he replied: "You're tired are you?"
"Are you tired?" asked the boy.
"Yes, I am quite tired too. Has it been a long day for you too? Have you been enjoying your chopsticks?"
"No," answered the boy.
"They are quite tricky I know," William grinned.
He told another little girl that she was very good at using her chopsticks.
"Thank you Your Royal Highness," she said.
"You've been briefed very well," William chucked. "The beans are quite tricky, they're quite slippery."
Downstairs the royal unveiled a plaque to mark the opening and gave a short speech in which he greeted the guests in Japanese, saying: "Minna sama. Konichi-wa."
He added: "This amazing building - Japan House London – is intended to be the bridge across which the best in ideas and creativity between the UK and Japan will flow. Here, we can build new and lasting relationships in culture, education and business and forge a better understanding of your wonderful country."
The prince then joined in a kampai toast - the Japanese equivalent of "cheers" – and drank from a small serving of Fukugao sake from Sanjo City served in a masu, a square, wooden sake cup used on celebratory occasions.
He was also presented with a silver hand-worked tea pot as a gift. Similar items sell in the shop for up to £8,000.