More than 100 guests were invited for canapes and wine in what used to be one of the agricultural barns at Llwynywermod, near Llandovery.
The hosts did not have to go far to greet the guests as the barn forms part of a courtyard adjoining their home.
The Duchy of Cornwall bought the Carmarthenshire estate in 2006.
Since then it has been given a major makeover.
One of those involved in the refurbishment was carpenter Tony Smith, who worked on the roof, stairs and doors.
He said: "If you go back a couple of months it was in a bit of a state really but it's come along really good.
On being invited to the royal function he said: "A night like tonight is something I will always treasure and remember for the rest of my life."
The evening was an informal occasion and the Prince of Wales and Duchess of Cornwall mingled casually with their guests.
This is the first week they have stayed at the estate which they bought as a base for their annual summer visits to Wales.
Also among the guests was local vicar Father Roy Doxsey.
He said: "It's great that he wants to meet the local people and is not hiding away up here. It's the first time most of us have seen it [Llwynywermod]. It's superb and it's really something for the area.
"In one way we are hidden away in Myddfai [the neighbouring village] and we like that but it's nice that he has come here and I'm sure he will enjoy the area.
"I think he will be coming here all the time now because the valley is not just peaceful here, it's so tranquil."
Nine people had a good time at our first Saturday morning jam session in Worthington. The weather was great, even though it looked bad on Friday.
So, come on out this Saturday morning, 9:30 - 11:30 to the South East Green, Rt 161 & High Street in Worthington. Bring a chair and a friend.