Cut lamb into cubes. Heat oil in a heavy saucepan, add lamb and cook until lightly browned, remove from pan. Add onion and garlic and cook for a few minutes. Add flour andd stir, heat until mixture browns. Gradually add stock while stirring. Return meat to saucepan. Add salt, pepper, rosemary and bay leaf. Cover and simmer for 1 hour or until meat is almost tender. Add potatoes, carrots and turnips. Cook 30 minutes longer. Add peas and onions and continue cooking until peas are tender, about 10-15 minutes.