10 lemons, 100g of sugar, one litre of bottled water, bottled fizzy water.
Dissolve the sugar in the water over low heat. Grate the lemon and put the zest (grated peel) into the sugar-water mixture. Let it cool. Squeeze the lemons and add the juice to the mixture. Pour the liquid into a clean bottle and keep it refrigerated. To serve, mix one part of this liquid with two parts of fizzy water and lots of ice, in a glass jug.