Trim away any fat or sinews and place each tenderloin between 2 sheets of cling film. Bash the tenderloin to flatten using the flat side of a meat mallet or a rolling pin, until it is about 1cm (½in) thick.
Combine the sausage meat, shallot, breadcrumbs and sage, mixing until well combined.
Lay the bacon rashers out on a sheet of cling film, so that they just overlap and form a large rectangle.
Place the flattened tenderloins on the middle of the bacon and pile the sausagemeat along the length of the fillet.
Use the other fillet to cover the sausagemeat stuffing. Pork fillets are usually thinner at one end so place the second one so that the thin end is at the thicker end of the first.
Bring the bacon up over the pork using the cling film for assistance. Roll the tenderloin so that it is encased in the bacon. Twist the end of the cling film to hold it in place and chill for about 1 hour or until required (up to 24 hours).
Preheat the oven to 200℃ (180℃ fan)/400°F /gas mark 6. Lightly oil the base of a shallow roasting tin. Remove the pork from the cling film and place in the centre of the pan.
Place the peppers and onion wedges along either side of the join and drizzle with a little oil. Roast in the centre of the oven for 50 minutes or until the bacon is crisp and the pork is cooked through (juices should she no trace of pinkness when you piece the meat with a knife).
Remove the meat from the roasting tin. Using a draining spoon remove the onion and peppers and place around the meat. Allow to rest in a warm place for about 15 minutes before serving.
Meanwhile to make the gravy.
Place the roasting tin over a low heat and stir in the sherry. Add the hot stock and bring to the boil, stirring to release all the juices stuck to the base of the tin.
Mix the corn flour with a little cold water. Add to the tin and stir constantly until sauce thickens slightly. Serve the pork cut into thick slices with the peppers and onions on the side. Pour the gravy into a jug and serve separately.
Nutrition information is approximate and is meant as a guideline only. (It does not include seasoning with salt and pepper.) Can be prepared 24 hours ahead of cooking.