Preheat oven to 120C (250F) fan forced. Or 140C (280F) for regular oven.

Place beans, onions, tomato, worcestershire sauce and ham hock in a large oven proof dish, preferably with a lid. Add 2 1/2 cups water and 2 tablespoons brown sugar if you prefer your beans a little sweet. Cover tightly with foil and the lid.

Bake beans for 8 hours, or until the beans are super tender and the ham is falling of the bone. If it looks a little dry, add some more water. If it looks too soupy, increase the oven temperature and cook uncovered until the sauce has reduced to your liking. Season well.