Wash artichokes thoroughly by first banging them hard on the counter-top to help open up. With your thumbs, force the leaves open and wash thoroughly. Immerse them in a large pot of cold water and let them soak while you prepare the stuffing.
Place peeled and quartered potatoes in base of slow cooker.
In a large bowl, add crumbled bread, capers, chopped garlic, parsley, olives, tomatoes, salt and pepper and oil. Mix well.
Remove artichokes from water, shake well any excess water. Cut off stem below about 2 inches from artichoke. With thumbs, force the leaves apart some more until you have a deep whole in the middle. Fill each up with all the stuffing equally. Press the stuffing right in so they are packed generously.
Add water to potatoes and place artichokes between the potatoes in a way that they won't tip over and loose the stuffing.
Cover and cook on High for 6 hours.