Dice all the veggies of the vegetable mix (except for peas) and set aside.
In a large pan add all the ingredients for the marinade, stir well and bring to a boil on medium heat.
Add the hard diced vegetables first (carrots, onions, peppers), and boil for 3 minutes. Next, add the remaining vegetables and boil for an extra 5 minutes. Finally add the peas and turn off the heat.
Allow the vegetables to marinate in the liquid for at least 30 minutes (for a milder pickled taste) up to 2 days (for a strong vinegary taste).
Boil the rice in salted water for around 15 minutes or according to packages instructions. Drain well and rinse under cold water.
Drain the marinated vegetables (you can re-use the liquid for pickling other vegetables).
To a large bowl add cooked rice, pickled/marinated vegetables, capers, olives (sliced), artichokes (chopped or sliced), vegan tuna (if using) and vegan mayo.
Stir it all together and place the vegan Italian rice salad in the fridge for at least one hour before serving.