As well as the senior test, young riders from each side of the Tasman will also go head to head. New Zealand has named Logan Massie (Dannevirke) on Kiwi Ludo (owned by Massie and Annette Scott), Rosie Commons on Glenara Chandon, Bridget Hansen (Ocean Beach) on Shakespeare NZPH and Melody Matheson (Hastings) on Cheltenham.
The Australians have sent Jack Maunder (New South Wales) on Cyra, James Arkins (New South Wales) on Dreamtime Invader, Nicole Bruggeman (South Australia) on Blusta and Sarah Beale (New South Wales) on Alpha Centuri.
The Holy Grail is a new initiative but challenge director Kevin Hansen is hoping it will become an annual clash.
"Spectators will be treated to something really special on Sunday."
He's encouraging families to pack a picnic and make the most of what promises to be a magical afternoon.
The action starts at 11.15am and goes through to 4pm.