warm large sterilised jam jars with screw tops - prepare jars by washing in hot soapy water and leaving to dry and warm in a cool oven - 130C/250F/Gas ½ for 10-15 minutes.
Put the vegetables into a non-metallic bowl. Sprinkle the salt over the top, toss together, cover and leave in a cool place for 12 hours.
The next day put the vinegar into a large saucepan or preserving pan, add the spices and bring to the boil.
Drain the vegetables and rinse well under running water for 3-5 minutes. Add to the simmering vinegar, cook over a low heat for 20-25 minutes or until the vegetables are tender. Add the sugar and continue to simmer for a further 1-2 minutes.
Mix 2 tbsp of cornflour with a little water and blend into the hot vegetables. Bring back to the boil and cook for a further minute, the mixture should be glossy and thick. Add the remaining cornflour in the same way if necessary.
Remove the piccalilli from the heat and leave to cool for 15 minutes. Spoon into the hot jars and cover with a disc of wax paper and a screw top lid, wipe the jars and label. Store in a cool dark place for 3-4 weeks before eating.