Preheat oven to 140°C.
Remove any giblets and clean the duck inside & out.
Prick the skin all over - but only the skin, not the flesh!
Rub the duck skin with oil and season with salt and pepper.
Cut the lemon in half and put inside the cavity together with the cinnamon, star anise and garlic.
Place the duck on a wire rack in a large baking tray.
Roast in the oven for 2 hours.
Meanwhile, peel potatoes, cut them in half and cook for 10 minutes in lightly salted water until just cooked. Rinse with cold water, drain.
Remove the duck to a plate from the oven and turn up the temperature to 200°C.
Pour the duck fat into a bowl then replace the duck in the middle of the tray.
Using a slotted spoon, dip the potatoes in the fat then put them around the duck, next to each other in the roasting tin.
Roast for about 30 minutes until the duck skin is crispy.
Transfer the duck to a large serving dish, cover it with foil and tea towels. Put the potatoes back in the oven and cook until golden & crispy - about 15-20 minutes more.
Put the potatoes and other roasted/braised vegetables around the duck and serve!