Firstly, depending on the thickness of your fillet, you may need to cut in half. It is best to have the thickness around 2 inches thick, so you can see in the photo, I sliced my piece of pork length ways. This will help to cook the pork quicker and also not burn or dry out.
Add ingredients to a zip lock bag and allow to marinade for at least 4 hours, better overnight.
Pour a shallow layer of water in the bottom of a roasting tin. I also like to line the tin with some heavy duty foil so it is easier to clean later. Place a roasting rack or wire cooling rack in the tin and put the meat on top, reserving the marinade. Brush some of the marinade over the pork.
Roast at 425 F or 220 C for 15 minutes, basting again half way through with the reserve marinade and turning the meat. Then place the meat under a HOT broiler / grill brushing over a little marinade. Turn often, whilst brushing more marinade so as to get a good glaze over the meat.
When the meat is cooked through, test by inserting a knife and checking the juices run clear, allow to rest for 15 minutes then slice and serve.