The Prince of Wales used a ceremonial sword to cut the cake at the official re-opening of one of Northern Ireland's most famous houses.
During the final day of their visit the Prince and Duchess of Cornwall toured Mount Stewart, a National Trust property in Co Down, which has undergone an £8 million refurbishment.
The house, on the shores of Strangford Lough is home to Lady Rose Loritzen, a distant cousin of the Duchess, whose family have lived there since the 18th Century.
Afterwards, Lady Rose said the Royal couple had been particularly impressed with the enhanced art collection which included paintings of the Duchess's ancestors.
She said: "They were very impressed.
"They really liked the house. His Royal Highness has been here before the restoration and I think he was really impressed.
"The Duchess sadly, couldn't come the last time so it was the first time Her Royal Highness had seen it and she loved it.
"Of course her family ancestors are mutual ones with me. A first cousin came over with William of Orange (and) there is huge portrait (of him) in the dining room and two portraits in our private sitting room.
"I think she enjoyed that too."
To slice the sponge cake which was iced with an image of Mount Stewart, Charles borrowed a silver sword from David Lindsay, Lord Lieutenant of Co Down.
Afterwards, the Duchess joked: "It's ruined."
The engagement which included a walkabout in the manicured Mount Stewart gardens provided some light relief for the Royal couple whose four-day visit has been heavily focused on peace and reconciliation.
Retired Church of England vicar Jim Bates from Ballyholme, Co Down was among the volunteers to speak to the prince.
He said: "He was very interested in the paintings and asked me whether the public were allowed in the house.
"I said that he had caused a bit of a log jam and he laughed."
During the hour-long tour the Royals viewed a well-known George Stubbs painting Hambeltonian which was displayed in a new frame above the staircase at Mount Stewart.
They also saw the Congress of Vienna Desk which belonged to Viscount Castlereagh when he was British foreign secretary at the close of the Napoleonic Wars and is said to have been used at the signing of the Treaties of Paris and Vienna in 1814 and 1815.
Before departing for Corrymeela peace centre in Co Antrim the couple signed the visitors' book and were presented with three Cedar trees.