The first-time father was all smiles as he walked around the grounds and chatted to local farmers, show-goers and judges.
When asked about his newborn, Prince William joked that the royal baby was "pretty loud and extremely good-looking," and added that there had been "just a few sleepless nights but [George] is sleeping much better now".
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Prince William and his wife Kate Middleton spent much of Kate's pregnancy in Anglesey, where he is based as a search and rescue pilot. It is largely thought that Wednesday's visit is the prince's official farewell to the island that has been his home for several years.
Addressing the crowds with a speech, the new father called Anglesey "an immensely special place for us both" and said the couple would be returning again and again with their new family.
Earlier on in the visit, Prince William watched gundog and falconry displays, and was presented with his own glove to take part in the show the locals had put on.
Watching the gundog display, he joked that he "should have brought Lupo for the spaniel show," referring to the couple's dog.
"He would have just run off and never come back again," the royal told ITV. "It would have been very embarrassing."
Kate and Prince George, meanwhile, have remained at her parents' home in Berkshire. With the recent birth of the royal baby, it is widely thought that Prince William will return to London where he can care for his new family. He will reportedly join his regiment, the Household Cavalry's Blues and Royals, which will allow him to carry out more royal engagements in support of the Queen.