Cut between the flesh of each pork rib bone so that individual pieces of meat are obtained and can be held in the fingers to eat after cooking. Sprinkle the meat with salt and place in a shallow roasting tin. Place in the centre of a moderately hot oven (200°C., 400 °F., Gas Mark 6) and roast for 30 minutes.
Meanwhile prepare the barbecue sauce. Heat the oil in a saucepan and add the onion. Fry gently until the onion is soft but not brown. Mix together the tomato ketchup, vinegar, sugar, mustard and Worcestershire sauce in a basin. Add this to the onion in the saucepan and bring up to the boil stirring well. Remove the sauce from the heat.
Lower the oven heat to moderate (180 °C., 350 °F., Gas Mark 4) and pour away any fat in the pan. Pour the barbecue sauce over the pork ribs and replace in the oven. Continue to roast the meat at the lower temperature for a further 1 hour. Baste often with the sauce. Towards the end the rib bones will become rather crisp and brown round the edges.
Serve the pork ribs with any sauce spooned from the roasting tin. Provide napkins and when cool enough to handle nibble the spicy meat off the bones.