Heat oil in the wok & add the garlic & walnuts. Fry stirring frequently till the nuts are slightly browned. Remove them with a slotted spoon. Add the prepared vegetables & cook till slightly softened. Stir in the rice & season to taste. Pour in the stock & bring to a boil. Cover, reduce heat & simmer gently for 10 minutes or so. Mix together the tomatoes & olives. Stir corn & peas into the vegetable mixture in the wok. Place tomatoes & olives on top, do not stir them in & replace the lid. Simmer for 5 minutes. All the stock should be absorbed. Before serving, stir in olives & tomatoes, nuts & herbs. Serve with a salad.