Heat the oil in a large pan over a medium-high heat. Add the onion, celery and carrot and cook, stirring, for 5 min.
Add the tomatoes, ham, stock and mustard and bring to the boil. Reduce the heat to low and simmer for 10 min or until the veg are tender and the soup has reduced slightly.
Add the lentils, beans, zucchini/courgette and peas and simmer for 5 min or until the beans are tender. Serve sprinkled with the parsley.