Heat the oil in a large, heavy-based pan. Add the onions and cook gently for 5 – 10 mins until softened. Add the garlic, spices, dried thyme, carrots, celery and peppers and cook for 5 minutes. Add the tomatoes, stock, courgettes and fresh thyme and cook for 20 - 25 minutes. Take out the thyme sprigs. Stir in the lentils and bring back to a simmer. Serve with wild and white basmati rice, mash or quinoa.