Slow-cooked Irish stew

Name: Slow-cooked Irish stew
Prep time: 20 min
Cook time: 8 h
Total time: 8 h 20 min
Cuisine: British, European
Ingredients: 1 tbsp sunflower oil; 200g smoked streaky bacon, preferably in one piece, skinned and cut into chunks; 900g cheap stewing lamb like middle neck or scrag (ask at your butcher counter), cut into large chunks; small bunch thyme; 3 onions, thickly sliced; 5 carrots, cut into big chunks; 6 medium potatoes, cut into big chunks; 700ml lamb stock; 3 bay leaves; 85g pearl barley; 1 large leek, washed and cut into chunks; small knob of butter