Combine sugar and water in a small saucepan over a low heat. Cook, stirring, for 3 minutes or until sugar is dissolved and mixture comes to the boil. Reduce heat to low. Simmer for 5 minutes. Remove from heat. Set aside to cool. When cold, place in an airtight container. Refrigerate.
Place 1/3 cup of chilled syrup, lemon juice, gin, mint, lemon rind and ice cubes in a blender. Blend until ice is crushed. Pour into 2 chilled glasses. Serve.