It will keep, sealed, for about a week in the fridge.
6 unwaxed lemons, finely zested and juiced
200g caster sugar
still or sparkling water, to serve
ice cubes, to serve
mint sprigs, to garnish
1. Put the lemon zest and juice and the sugar in a saucepan with 450 ml water. Stir well. Bring slowly to the boil. Simmer for a minute or two and stir to ensure the sugar dissolves completely.
2. Remove from the heat and allow to cool. Strain into a clean bottle and store in the fridge. Dilute 40:60 with chilled still or sparkling water, or to taste. Garnish with mint sprigs and serve with lots of ice.