Place the vegetables in a large glass bowl and sprinkle with the salt. Stir lightly then cover and leave overnight; this draws out some of the moisture and makes the vegetables crisper.
The next day, rinse well and drain in a colander. Mix the flour and mustard powder with a little vinegar to make a smooth paste. Place the vegetables in a preserving pan and add the remaining vinegar, all the spices and the sugar. Bring to the boil, then reduce the heat and simmer for 10 minutes.
Add the flour and mustard mixture to the pan and stir well until thickened. Simmer for 2-3 minutes, then remove from the heat and spoon carefully into clean, dry, sterilised jars, before sealing and labelling them.
The piccalilli can be eaten after a week, but is better if left for a month before eating. It will keep for 6-9 months.
Nothing beats making your own piccalilli to go with ham, cheese or a traditional ploughman's lunch. You can vary the vegetables - add more or fewer runner beans or carrots, use French beans, or add green tomatoes or diced cucumber instead.