Use a large sealable food bag and mix the sea salt and 200g of the sugar.
Add the pork and coat it well, rubbing everything in. (If you don’t have a bag, rub over the pork in a dish and cover with cling film.)
Leave in the fridge overnight.
Preheat the oven to 140°C / 275°F / Gas mark 1.
Sit a rack on a roasting tin and set aside.
The next day, remove the pork and wipe down the meat with kitchen paper.
Mix the remaining sugar, the maple syrup, mustards and some ground pepper.
Rub half the mixture over the pork and sit it on the rack.
Roast for 6 hours.
Spoon the remaining maple mixture over the pork and roast for 1 hour more.
Rest the meat for 30 minutes on a plate loosely covered with foil.
To serve, pull the pork into big fat chunks using 2 forks and, after skimming the surface, spoon over any juices from the roasting tin.