Add the blackberries to the pot and some water so it just covers the fruit.
Boil the fruit until soft and the water partially evaporated. This will take approximately 15 to 20 minutes.
Add the sugar and lemon juice and boil until the mixture has reduced by half (about 20 - 30 minutes).
Take a teaspoon of jam and spread on the cooled plate. Leave it for a few minutes. If the jam has skin on it or pulls slightly with your finger, it’s ready!
Pour into sterilised glass jars and quickly seal. Leave to cool. The lids should pop (if you have poppable lids), which means they are properly sealed.
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