Place the ice cubes, whisky, lemon juice and sugar syrup in a cocktail shaker: shake vigorously.
Strain into a chilled glass.
Garnish with a slice of lemon and a maraschino cherry. Serve immediately.
Sugar syrup: Combine 220 g caster sugar with 250 ml water in a small saucepan over a low heat. stirring until the sugar dissolves, then bring to the boil. Reduce the heat; simmer, uncovered, for 5 minutes. Cool. Store in the refrigerator, in an airtight container, for up to one month. Makes 50 ml.