Easy Christmas roast duck with crispy potatoes & port gravy

INGREDIENTS

• a few sprigs of fresh rosemary
• ½ nutmeg, grated
• sea salt
• freshly ground black pepper
• 2 oranges or blood oranges, zested and halved
• 2 x 2 kg whole ducks, necks and giblets reserved and roughly chopped
• 8 cloves garlic, unpeeled
• 3 red onions, peeled and quartered
• a few stalks celery, trimmed and chopped into chunks
• 3 carrots, scrubbed and chopped into chunks
• ½ stick cinnamon
• 1 thumb-sized piece fresh ginger, peeled and roughly chopped
• a few bay leaves
• 2 kg Maris Piper potatoes, peeled and cut into large chunks
• 1 litre water or organic chicken stock
• 2 tablespoons plain flour
• 200 ml red port