In a saucepan, add the vinegar, red wine, and brown sugar and stirring, bring to a boil. Have a glass measuring cup ready to measure. Reduce the heat and simmer rapidly until liquid reduces to 2½ cups, about 40 minutes. Add the prunes. Continue to simmer the sauce until it reduces to 2 cups, about 20 more minutes. Then continue to simmer for about 10 more minutes until the sauce is black, syrupy, and glossy. Be careful that the sauce does not over-reduce and burn. Serve alongside the Pork Roast.