Put the vegetables into a large non-metallic bowl and massage in the salt.   Cover with a tea towel and leave for 6 hours.   This will help draw water from the vegetables, preventing a watery piccalilli while also intensifying the flavour.

After 6 hours, rinse the veg well under cold running water to remove the salt, then pat dry with kitchen roll.

Tip the coriander seeds, mustard seeds and cumin seeds into a large pan.   Toast over a medium heat for 1 to 2 minutes, or until fragrant, then whisk in the turmeric, mustard powder, sugar and cornflour.   Add 100ml of the cider vinegar and stir until you have a smooth, glossy paste.   Gradually add the remaining cider vinegar until you have a smooth sauce.

Add in the vegetables and cook over a medium heat for 10 to 15 minutes, stirring occasionally, until the veg is just starting to soften on the outside, but retains its crunch.   Turn off the heat and let the piccalilli cool in the pan for 10 minutes.