1.Combine sugar, 1 cup juice and glucose syrup in small saucepan, bring to the boil. Stir over medium heat until sugar dissolves, cool. Stir in lemon juice, 2 cups grapefruit juice and Campari. Churn in an ice-cream maker, according to manufacturer’s instructions; freeze for 4 hours. Serve scoops of sorbet in cocktail glasses topped with Champagne or sparkling white wine.