Peel the lemon with a sharp knife, then cut the peel in thin strips.
Soak the peel overnight in water, then simmer for about 30 minutes or until almost soft.
Add about 2 tablespoons lemon juice, the blueberries and sugar to the lemon peel.
Cook over low heat, stirring frequently, until the juice will run off the spoon in 2 drops or until almost to the jellying point.
Remove from heat and let cool to room temperature.
Stir to keep the blueberries and peel distributed, then ladle into jelly glasses or jars and seal.