Put the caster sugar, rhubarb, orange and star anise in a pan with the water. Bring to a simmer and cook gently for 5-6 mins, or until the rhubarb is soft and the sugar has dissolved. Remove from the heat, leave to cool and strain into a jug. (See tip below.)

Pour 100ml of the syrup into a mixing glass or a jug with the lemon juice, rosé and ice. Stir well until the mixture has chilled, then strain into two wine glasses over ice. Top up with soda water, taste and add a dash more syrup, if you like. Garnish each with a peeled rhubarb ribbon.