Top and tail the beans and slice them diagonally. Put them in a bowl and sprinkle each layer with salt, then leave them for 1 hour to soften. Rinse off the salt (taste a bean to make sure) before you continue to cook them. Dry the beans on a tea towel then put them in a large heavy pan with the oil. Peel and chop the onion. Chop the tomatoes and add to the pan with the onion, oregano and plenty of pepper. Pour on boiling water to almost cover the beans then bring them to simmering and cook them for 25 to 30 minutes or until they are tender. (The beans for this recipe should be cooked until they are a little softer than you would usually serve them but make sure the sauce is thick.) Stir in the parsley and serve warm with crusty bread as a starter, allowing 1 ounce per person, or without the bread as a vegetable.