Preheat the oven to 180°C/350°F/Gas 4.
Taking a sharp knife, score the skin of the pork 12 to 15 times.
Rub the vinegar over the skin, mix together the salt and thyme and rub into the skin.
Place on a roasting tray and roast for 1½ hours basting every 15 minutes or so.
After about an hour, pour some of the fat juices into another tray and heat until smoking hot. Season the potatoes with salt and add them to the hot fat, spooning it over to make sure each piece is covered. Cook until crisp and brown, which will take about 40 minutes, turning occasionally.
Whilst the meat is in the oven, pre-cook the vegetables separately in plenty of boiling salted water. Begin with the cauliflower, remove and plunge into cold water. Do the same with the carrots, beans and broccoli - in this order. Once they are all cooked and cooled, set aside until needed.
Once the meat is cooked, remove from the tray and leave to stand. Pour off the excess fat.
Place the oven tray on the stove, add the marmite, red wine and stock. Reduce, add half the butter and seasoning before passing through a sieve. Keep warm until needed.
To serve, remove the roast potatoes and transfer to a serving dish. Reheat the vegetables in boiling salted water, tip into a serving dish and dot with butter. Remove the crackling, break into pieces and carve the meat. Pour the gravy into a jug.