In a saucepan over medium heat stir together the sugar and water. Let come to the boil, then add the blackberries and simmer for a couple of minutes or until the sugar has completely dissolved. Remove from the heat, and leave to infuse for 30 minutes.
Strain the mixture into a large jug and add the wine. Mix well then pour into a freezer safe container and freeze for about an hour. Using a fork, scrape and stir to break up the icy crystals, then return to the freezer for a further 8 hours, scraping and stirring every hour or so.
