Prince Charles and the Duchess of Cornwall were in the region to tour the property and grounds on Saturday.
It was a chance for the Prince, President of the National Trust, to show his support for saving the Grade One listed building from private sale.
A handful of royal supporters stood at the roadside in bright sunshine as the couple were driven through the gates at about 11.30am.
Youngsters waved flags as the visitors smiled and waved back through the open window of the car.
Julie Farthing, of Seaton Sluice, was pleased to see royal acknowledgment of the project to save the hall.
She said: "It's really nice of them to come and see the grounds. It's a beautiful place, it really is.
"You never used to see many cars around here, but since the campaign has been launched to save it, it has become more popular.
"Having Prince Charles and Camilla supporting it is great."
During their visit the couple thanked members of the local community and supporters of the National Trust.
Nancy Dixon of Seaton Delaval was delighted to see them.
"It's very nice to see them come here," she said. The building has been in families for generations around here and it's lovely to see them show their support for it."
The National Trust is bidding to buy the Hall and its 450 acres of grounds for £6.3m from Lord Hastings.
The hall has been described as one of the finest examples of the work of Sir John Vanbrugh, architect of Blenheim Palace and Castle Howard in Yorkshire.
The National Trust has raised £3m with donations, £1m will come from the regional development agency One North East, and a further £2m could be raised if Lord Hastings and the Government come to an agreement over inheritance tax owed following the death of his parents in 2007.
That leaves the Trust £300,000 to raise, and it has launched a campaign to find the rest.
The couple enjoyed Caribbean dancing by a group of young people called Dance Kaleidoscope.
Director Gillian Quinn, from Whitely Bay,said afterwards: "They really enjoyed performing for royalty, they were very keyed up."
You can make a donation to the campaign fund at
www.nationaltrust.org.uk/seatondelaval or call 0844 800 1895.
Or cheques can be sent to Save Seaton Delaval Hall, the National Trust, PO Box 39, Warrington, WA5 7WD.