Put all the ingredients in a large saucepan or stainless-steel or enamel preserving pan and simmer, stirring frequently, for about 1 1/2 hours, or until the relish is thick and leaves a clear trail when a wooden spoon is pulled across the base of the pan. Do not allow the relish to cook too quickly or it will stick to the pan.
Spoon into clean, warm, dry jars and cover immediately with vinegarproof lids. Label and date when cool. Store in a cool, dark, airy cupboard and use within two months.