In a saucepan over a medium heat, warm the oil and add the onion, carrots and celery. Cook and stir for 5 minutes until just soft, but do not allow to brown. Add the peas, bay leaf, vegetable stock and water. Season well. Cover and cook for 1 hour over a low to medium heat, until the flavours have developed and the vegetables are soft. Remove and discard the bay leaf. Serve in hot bowls topped with fresh herbs.