4 large limes
125g caster sugar
2liters cold spring water or sparkling mineral water
1. Halve one of the limes crossways and set one half aside.
2. Take the remaining 3 1/2 limes and juice them. Pour the juice into a large jug, add the caster sugar and stir to dissolve.
3. Take the remaining half lime and slice into thin rounds. Top the lime juice and sugar mix with chilled spring water or sparkling mineral water.
4. Garnish with the slices of lime and serve.