Simmer apples, cranberries, and cinnamon in enough water to cover for 15 minutes.
Strain the mixture through a muslin-lined sieve and discard the remaining pulp.
Add 500g of sugar for every 600ml of collected liquid.
Boil the liquid slowly until it reaches 105°C on a sugar thermometer.
Pour hot jelly into warm sterilised jars and let cool to set.
Preheat the oven to 180°C.
Brown the seasoned pork loin in olive oil in a frying pan.
Roast the pork in a tin for 60 minutes until the crackling is golden.
Carve the pork and serve with a spoonful of the prepared jelly.