The first in line to the British throne spent time with his son Prince Harry and his wife Meghan, Duchess of Sussex's 12-month-old daughter and three-year-old son Archie while the family were in the UK for Queen Elizabeth's Platinum Jubilee at the start of June.
And the 73-year-old future king was overjoyed to finally get to meet Lilibet Diana Mountbatten-Windsor, affectionately known as Lili, and to see Archie again after some time.
A senior royal source said: "It was fantastic to see them. It was wonderful to have them back in Britain.
"The prince and the duchess were absolutely thrilled to see them.
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"The prince, of course, hasn’t seen his grandson Archie for a bit of time and so it was very, very, very special to have some time with him.
"He hadn’t met Lili, his granddaughter, and so to meet her was very emotional, a very, very wonderful thing."
Harry and Meghan attended a thanksgiving service at St Paul’s Cathedral as part of the Jubilee celebrations.
The 96-year-old monarch also got to meet her great-granddaughter, who celebrated her first birthday during the stay, for the first time.
The Duke and Duchess of Sussex now live in Montecito, California, after stepping down as senior members of the Royal Family.
Harry, 37, Meghan, 40, and their children stayed at Frogmore Cottage in Windsor, and Queen Elizabeth is said to have wanted their visit to help heal the family rift, which has widened since they quit as senior royals and complained about Harry's family in a televised interview with Oprah Winfrey.
A source explained to The Daily Mail newspaper before the visit: "Her Majesty is typically very keen that the Platinum Jubilee be a celebration not of herself and her own longevity, but of the institution of the monarchy and the people that support and sustain it.
"It is also a chance for people to come together after a very difficult period for this country. She doesn't want anything to overshadow it – and that includes any family issues."