Put the barley in a pot and cover with cold water. Bring to a boil, and then let boil for a further 3 minutes. Strain.
Put the barley in a jug with the sugar and the peel of the lemon, add 2 cups / 1 pint of fresh boiling water (not the water you discarded.)
Let stand until cold. Then strain and discard the solid material, keeping just the water.
Serve plain in glasses, or flavour with juice from the lemon and / or sugar. You can also serve it with ice cubes; sometimes it was diluted half/half with milk.