Place the loin of bacon in a saucepan and cover with cold water. Add in the celery, onions, thyme & black peppercorns. Bring to the boil, then reduce the heat and simmer gently for 20 minutes per 450g. This can be cooked a day in advance and allowed to cool and store in the fridge.
Preheat the oven to 170°C (340°F/gas mark 3). Carefully peel away the skin, leaving the layer of white fat intact. Using a sharp knife, score the fat diagonally to make a diamond pattern, being careful not to cut into the meat. Stud the diagonal with cloves.
Place all the ingredients into a high sided saucepan. Bring to the boil and allow to boil for 5-6 minutes until reduced to a syrup consistency. If the syrup is too thick, add a tablesppon of water. Transfer to a jar and allow to cool. Use as required. Brush a layer of the syrup all over the bacon loin, reserving the remainder. Cook for 30-40 minutes, brushing over another layer of the glaze every 15 minutes, until it’s all gone. Remove the cooked bacon loin from the oven, transfer to a serving platter and leave to rest for 15 minutes.