Put the prepared vegetables into a large non-metallic bowl, then dissolve the salt in the water and pour over the vegetables.
Leave to stand for 24 hours covered with a cloth, then drain thoroughly.
Mix together the flour, mustard, turmeric, cayenne pepper and sugar and stir in a little of the vinegar to make a smooth paste. Gradually add the remaining vinegar and put the liquid into a preserving pan.
Bring gradually to the boil, stirring until the mixture thickens. Add the drained vegetables and boil for 5 minutes or until the vegetables are heated through.
Pack into sterilised jars and cover tightly. Keep for at least 2 weeks before using.