Spray a large saucepan with low-calorie cooking spray and place over a medium heat. Add the onion, leek and garlic and cook for 5 minutes until starting to soften.
Add the chicken, carrot, pearl barley, bay leaves, thyme and stock and stir well. Bring to the boil, then reduce the heat to a simmer, and cover with a lid. Cook for 30-35 minutes, or until the pearl barley is tender and the soup has thickened slightly.
Remove the bay leaves and season to taste with salt and black pepper, if needed. Serve alone or with a crusty wholemeal roll or other accompaniment of choice.