1.Combine sugar and the water in medium saucepan; stir over low heat until sugar dissolves. Add rind; bring to the boil. Boil, uncovered, without stirring, 3 minutes. Transfer hot syrup to large heatproof jug.
2.Add juice to syrup; stir until combined. Pour syrup through fine sieve into sterilised bottles; discard solids. Cool to room temperature.
3.Just before serving, mix by adding four parts still or sparkling mineral water to one part lime syrup, or to taste.
The lime syrup will keep in the fridge for up to two months. Add a few drops of green food colouring to the syrup, if you like.Note