Remove any stalks from the berries and soak overnight in lemon juice and gin.
In a large heavy based saucepan combine the berries and sugar. On a low to medium heat slowly bring to a boil and continue boiling for about 20 minutes. Stir occasionally to avoid sticking.
The jam is ready when the mixture has thickened a little. Drop spoonfuls onto a saucer to check the setting point.
Pour the hot jam into sterilised jars and seal.