Preheat the oven to 200C/400F/Gas 6. Using a sharp knife, score the skin of the pork 12 to 15 times.
Place the pork in a colander in the sink and pour boiling water over the scored skin - this is to help achieve perfect crackling.
Put the pork, skin-side up, in a roasting tin, drizzle with a little oil and sprinkle over some salt. Scatter over the sage leaves and add the lemon halves.
Roast the pork for approximately 1½hours or until cooked through. The juices will run clear when the meat is pierced with a skewer when cooked through.
Meanwhile, for the potatoes, melt the butter in a medium saucepan. Sauté the potatoes with the thyme and garlic for 10 minutes or until golden and cooked through. Season well with salt and freshly ground black pepper.
For the sauce, put the apples in a pan with the butter, water, vinegar and spices. Cover and cook until softened but chunky. Add sugar to taste.
Serve the pork cut into portions with the spiced apple sauce and the thyme and garlic sautéed potatoes.