100 grammes pearl barley
Copious amounts of water (so you have at least 1 litre left after
boiling)
3 lemons
3-4 oz white sugar (to taste)
Boil your barley in the water for about 20 minutes until it is soft. Strain, reserving 1 litre of the water, and use in another recipe, or discard, or whatever.
Meanwhile, remove the lemon-peel with a potato peeler (don't get any of the white pith if you can help it), and place in a heatproof jug along with the sugar. Pour on boiling water to cover, and stir vigorously until the sugar is dissolved. Then add the juice of the lemons, and top up with the barley-water until it is the strength you like. Add some ice-cubes to bring it to a drinkable temperature, and keep in the fridge. Stir before pouring, and, if it's for medicinal purposes, get it down you!