Brown Lentil and Vegetable Soup

Oil
2 carrots, diced
2 zucchini, diced
2 sticks celery, diced
1 onion, finely chopped
400g can tomatoes
2 C vegetable stock
400g can brown lentils, rinsed, drained
Salt and pepper
Heat oil, cook carrots, zucchini, celery, onion 10 mins. Add tomatoes and stock, bring to boil, reduce heat and simmer partially covered 15 mins until all soft. Add lentils, cook 5 mins until heated through. Season.