Skin the tomatoes. Peel, core and slice the apple. Peel and slice the onion. Wash the sultanas and dates in hot water before chopping. Remove the trivet from the pressure cooker, then put in these ingredients. Add the spices, tied in a muslin bag, the salt and ¼ pt. of the vinegar. Bring to 15 lb. pressure and cook for 10 min. Allow pressure to reduce at room temperature. Add the rest of the vinegar and the sugar and stir until the sugar is dissolved. Bring to the boil and simmer gently, in the open cooker, until thick. Pour into hot jars and seal immediately.