Place the blackberries, caster sugar and water in a medium saucepan and cook over a medium-low heat, covered, stirring occasionally until soft; usually 10 minutes. Remove from the heat and purée using a stick blender.
Pass through a fine sieve and collect the purée in a bowl beneath. Dilute to the consistency of a thin syrup using water. Allow to cool.
Pour into lolly moulds and replace with the handles with lolly sticks in place. Freeze overnight and serve when ready.
Freezing and defrosting guidelines
In order to enjoy optimum flavour and quality, frozen items are best used within 3 months of their freezing date. For more tips on freezing food, read our article Love Your Freezer.