With a sharp knife, slash 2-3 deep slashes in the side of the fish to ensure quick and even cooking. Stuff the cavity of the fish with grape clusters, citrus slices and mint. Secure the belly of the fish closed with a toothpick or wooden skewer. The fish can be held like this for up to 24 hours before cooking.

Preheat a grill to medium-high heat. Clean the grill grate well. Rub or brush the outside of the fish with vegetable oil and season with plenty of salt and pepper. Grill the whole fish on each side for 4-5 minutes or until the skin has crisped and the flesh is white and tender. Remove from the heat. Discard the toothpicks or skewer and serve with Grape and Mint Relish.