As soon as you can, season the pork all over with 1 tbsp of the salt. Up to 48 hrs before is perfect but if you don’t have time, don’t worry. Keep the salted pork covered and chilled.
In a mortar with a pestle (or finely chop with a knife) crush the garlic, thyme and bay together to make a paste and mix generously with some more salt and plenty of pepper. Lay the pork skin-side down on a chopping board, score the flesh in a criss-cross pattern all over and massage the herby seasoning into the flesh. Starting from the longest side, roll the belly up as tightly as you can into a joint surrounded by the skin, then use butcher’s string to tie the joint tightly at regular 2cm intervals to hold the joint together. If you can do all this the day before, all the better, then leave the joint to cool in the fridge ready to be roasted. This can be prepared up to 48 hrs before or three months before and frozen – defrost completely before cooking.
When you’re ready to cook, heat oven to 160C/140C fan/gas 3. Place a wire rack or trivet over a large roasting tray and sit the pork on top. Massage or brush the pork skin with the oil and give it a final sprinkling of salt. Roast for 3 hrs, basting with the fat every 30 mins after the first hour.
Remove the pork from the oven and turn up the heat to 240/220C fan/gas 9. Pour out most of the fat from the tray and tip in the peppers, chillies, shallots, garlic and tomato. Place the pork back on the wire rack and roast everything for a further 30-40 mins, turning the joint with tongs to expose different parts of the skin to crisp up the crackling and roast the vegetables. When the pork is ready, lift onto a board and rest for 10 mins ready to carve.
Scrape all the vegetables and pan juices into a mini chopper or smoothie maker with the vinegar and honey and a pinch of salt. Pulse to a sauce as chunky or smooth as you like. Carve the roast into slices with a serrated knife and serve in buns with the chilli sauce for spreading over.