For the pork, preheat the oven to 230C/475F/Gas 8.
Bring a kettle of water to the boil. Place the pork on a metal rack suspended over the sink or a bowl and pour the boiling water over the pork, allowing to drain.
Pat the pork dry with kitchen paper, then rub all over with the olive oil and season, to taste, with the salt flakes and freshly ground black pepper. Roll the pork into a neat cylinder and tie with butchers' string.
Place the pork into a roasting tray and roast for 30 minutes.
Reduce the oven temperature to 180C/350F/Gas 4 and cook the pork for a further 1-1¼ hours, or until the crackling is crisp and the meat is tender and cooked through.
Meanwhile, for the roasted apple, place the apples onto a roasting tray.
Mix the spices together in a bowl, then sprinkle the mixed spices over the apples and stir to coat.
Dot the butter over the top of the apples and then pour over two tablespoons of water.
Place in the oven with the pork and roast for 20 minutes, or until the apple is tender. When ready to serve, roughly mash with a fork, add sugar and seasoning, to taste.
For the mash, place the potatoes into a pan of salted water and bring to the boil. Reduce the heat and simmer for 12-15 minutes, or until the potatoes are tender.
Drain the potatoes and return to the pan. Place over a low heat for one minute to dry off any excess moisture.
Mash the potatoes well or pass through a ricer into a clean saucepan.
Meanwhile, place the butter and milk into a saucepan and bring to a simmer, then beat the butter and milk into the mashed potato. Season, to taste, with salt and freshly ground black pepper.
For the greens, heat a separate frying pan until medium hot, add the butter and 50ml/2fl oz water and bring to a boil, then add the spring greens and fry until just wilted. Season with a touch of salt, black pepper and ground nutmeg.
Remove the pork from the oven, place the meat onto a plate and set aside to rest for 15 minutes. Bring the juices in the roasting tin to a simmer over a medium heat.
To serve, carve the pork into slices and serve with some mash, the spring greens and a dollop of roasted apple. Finish with a drizzle of pan juices.