1. Measure the sugar into a bowl.
2. Mix the pectin with the juice, port and water in a five- to six-cup saucepan. Stir until the pectin has dissolved. Place over high heat and stir until the mixture comes to a full rolling boil.
3. Add the sugar at once and return to a hard boil. Boil one minute, stirring constantly.
4. Remove the jelly from the heat, skim off the foam and pour at once into hot sterile glasses. Seal with paraffin.