2.Heat light olive oil in a 6-litre (24-cup) flameproof baking dish; cook lamb, in batches, until browned all over. Remove from dish.
3.Add onion, carrot and celery to same dish; cook, covered, over low heat, stirring occasionally, until soft. Add garlic, stock, wine, paste, barley, lentils, chickpeas and thyme; bring to the boil. Return lamb to dish, cover; cook, in oven, for 2 hours. Stir in the water; roast, covered, for 1 hour or until lamb is almost falling off the bone. Season to taste.
4.Meanwhile, combine tomato, juice, extra virgin olive oil and half the parsley in a small bowl; season to taste.
5.To make tzatziki, squeeze excess liquid from cucumber; combine cucumber with remaining ingredients in a small bowl. Season to taste.
6.Serve lamb topped with tomato salad and tzatziki; sprinkle with remaining parsley. Serve with warmed or grilled pita bread.
To freeze: complete recipe to the end of step 3. Pack into freezer-proof containers, leaving a 2.5cm (1 inch) space to allow for expansion. Seal, label and freeze for up to 3 months. Thaw overnight in the fridge. Reheat in a saucepan or microwave on medium power (50%) until heated through.