Roll the pork fillet in the seasoning until well covered.
Heat the oil in the pan, add the pork fillet and cover with lid. Turn frequently until browned on all sides, (replacing lid after every turn) then reduce heat a little.
Peel and quarter the potatoes, roll in any left-over jerk seasoning, and place in the pan with the pork fillet, replacing lid. Shake the pan from time to time to make sure nothing is sticking to the base of the pan, and turn the potatoes so that each side crisps. Both the pork and the potatoes will be done within half an hour.
Remove the pork to a plate or tray for carving, serve potatoes on to warmed plates, and quickly stir 1/4 cup water in to the pan to make a light gravy.
Cut the fillet on the diagonal into 1cm thick slices, serve with vegetables, and spoon the gravy over.