Gwrych Castle vandalised ahead of filming for I'm a Celebrity... Get Me Out Of Here!
The castle being used as the site for I'm A Celebrity... Get Me Out Of Here! was vandalised just hours before it was handed over to the programme makers.
The ITV reality show is returning to Gwrych Castle for a second successive year after the pandemic forced producers to abandon plans to film in Australia.
One member of staff told PA they witnessed three children "demolishing the battlements."
He said he was "astonished", adding: "Thankfully nobody was injured, but part of the Grade-I listed building was damaged."
One of the castle's restored battlements on the east lawn was left damaged after the incident on Sunday.
A message posted on the castle's Twitter account said: "Our final day reminded us how far we've come, but also how much we have left to do over the coming years.
"It was a huge shame to see that somebody damaged one of the restored battlements on the east lawn on our last day.
"This goes to show the huge task we have ahead of us!"
The trust said the castle has previously experienced arson attacks, vandalism and theft.
A representative for the trust said: "We believe that it's important that people are aware that even in the 21st century, historical landmarks are still being damaged and left to deteriorate."
The castle confirmed it closed to the public on Sunday due to hosting the ITV programme and would not reopen until 2022.
The move from Australia to the Welsh location will help the ongoing restoration of the castle, according to Mark Baker, chair of the Gwrych Castle Preservation Trust.
Ant McPartlin and Declan Donnelly will return to host the upcoming series of I'm A Celebrity... Get Me Out Of Here!
McPartlin previously said he would be "very happy" for the programme to return to Wales.
The last series of the programme was won by podcast host Giovanna Fletcher.
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