Put the barley in the water and bring to a boil. Add the sliced apples and continue cooking gently until the barley and apples are soft. Press through a sieve, or put through the blender, and put back in the saucepan.
Add the sugar and lemon juice and bring to the boil again. Remove from the heat, allow to cool, and then chill.
Serve cool with the cream stirred in.