Heat oil in a large heavy-bottomed pot and seal lamb all over. Remove and set aside.
Add a little fresh oil to the pot if needed and gently saute carrots, onions, swede, celery and garlic until reasonably tender, stirring now and again.
Then return the lamb with any juices, together with tomatoes, 4 litres stock, soy, sambel, seasonings and barley. Turn heat down, stir well and simmer until lamb is very tender, skimming as necessary and adding more stock if needed. Taste for seasoning.
When almost ready, add peas and parsley.
NB: If freezing the soup, add the peas and parsley when reheating.