Charles and Camilla will meet staff, exhibitors and award-winning livestock and will tour many of the events on the first day of the agricultural show in Harrogate, North Yorkshire.
Other famous guests attending the 157th show include the BBC’s The One Show presenters Alex Jones and Matt Baker, Blue Peter presenters Barney Harwood and Radzi Chinyanganya, and TV celebrity chef Rosemary Shrager.
The Great Yorkshire Show, organised by the Yorkshire Agricultural Society, is billed as England’s premier agricultural event and is expected to welcome around 130,000 visitors over three days.
It features the best of British farming, with demonstrations, exhibitions and competitions from show-jumping to sheep-shearing. This year there will be more than 1,200 stands and almost 13,000 competition entries.
The Prince, who became patron of the show in 1998, and the Duchess will be presented with a white rose buttonhole and a posy by Kate Donnelly, five, and four-year-old Jessica Fox.
Jessica, from Thirsk, North Yorkshire, first visited the show when she was just two weeks old.
Her mother, Lynsay, said: “Jessica is busy practising her curtsies at home, they are a bit wobbly at the moment. She is very much looking forward to meeting the royal couple.”
Kate’s mother Emma said her daughter, a pupil at Hookstone Chase Primary School in Harrogate, was very excited about her role.
She said: “Kate loves anything to do with the royal family and she is already visiting Buckingham Palace with her grandmother later this summer so this has meant her excitement levels are at an all-time high.”
The Prince will have the chance to view some of the work carried out by charities close to his heart.
He will meet representatives from Bell View, a community charity supported by The Prince’s Countryside Fund, which provides home care and services to older people living in Northumberland.
As part of the Land Rover Bursary scheme launched by the Prince in 2013, Bell View was recently awarded a new car to help access remote and isolated communities in winter.
Charles will also visit the stand held by the Rare Breeds Survival Trust, which he has been patron of since 1986.
Bill Cowling, the outgoing show director, said: “The Prince of Wales is of course our patron and I have had the honour of showing our wonderful farming showcase to His Royal Highness and The Duchess of Cornwall on several occasions.
“Their presence always creates a very special atmosphere as it is plain to see how much they enjoy meeting our visitors and they have a genuine interest in our show and farming generally.”
Visitors to the show on Wednesday will be able to watch two BBC programmes being filmed.
The One Show will broadcast live from the event, while Blue Peter presenters are recording a future episode featuring a One Man And His Pig competition and the Young Stock Handlers section of the show.
The Great Yorkshire Show takes place at the Great Yorkshire Showground, Harrogate, from Tuesday July 14 to Thursday July 16.