Place pork, onion, 1 chilli (halved), carrots, bayleaves, 2 rosemary sprigs, vinegar and salt in a saucepan large enough to hold pork. Cover with cold water and bring to the boil. Cover and simmer 90 minutes. Leave to cool in the liquid then proceed, or refrigerate for up to 2 days.
Preheat oven to 170°C/340°F/Gas Mark 3-4. Take pork from liquid, strain off 400 ml (13 ⅔ fl oz) and discard the rest. Place pork in a casserole dish large enough to hold it and pour on the reserved liquid. Tuck remaining rosemary into the pork and add olives, remaining chilli (sliced), raisins and golden syrup. Cover and bake 45 minutes, then remove lid and roast until liquid has become almost a caramel. Remove pork from pot, take off the string and slice pork about ½ cm (¼ in) thick. Dollop some mash on the plate, sit sliced pork on, then spoon on the olive mixture.