1/2 cup water
juice of 1 lemon
Combine blackberies, water and lemon juice in a large saucepan. Bring slowly to the boil and cook for 5 minutes. Add sugar, bring back to the boil, stirring until sugar is dissolved. Boil for 20 minutes or until setting point is reached.
Leave to stand for 5 minutes, then pour into warm sterilised jars and seal.