3 tbsp caster (superfine) sugar
150ml/¼ pint/scant ⅔ cup freshly squeezed lemon juice
150ml/¼ pint/scant ⅔ cup freshly squeezed lime juice
150ml/¼ pint/scant ⅔ cup gin
1 Rub half a lemon around the rim of each of six glasses. Put 1 tbsp sugar on a saucer and press the rim of each glass into the sugar.
2 Put the lemon and lime juices in a cocktail shaker or screw-topped jar with the remaining sugar and the gin and shake vigorously.
3 Cut the remaining lemon into six slices.
4 Serve the gin sling over ice, topped up with soda water.