Heat the oven to 180°C / 350°F / Gas 4. In a small dish mix together the lemon juice, rosemary, two tablespoons of the olive oil, salt and pepper. Trim the pork tenderloins if necessary, discarding excess fat. Cut off the silver skin (see picture), then roll the tenderloins in the marinade until well coated and set aside.

In a large frying pan heat the remaining oil until hot but not smoking. Add the tenderloins to the pan and brown well on all sides. It’s alright if they are curled up a little to fit the shape of the pan. Browning should take around 5-10 minutes. If you don’t have a big enough pan, just do this in two lots.

Meanwhile cut two large sheets of tin foil. When the tenderloins are nice and brown, place each on one of the sheets (you can double line this with baking paper if you like). Stir together the parsley, oregano, garlic, and orange zest and rub over the pork. Season again with salt and pepper, then top each with a few slices of butter, and scatter over the chopped orange. Wrap in the foil, leaving a little room above the pork for the steam, and pinch the foil tightly closed to seal.

Transfer to an oven tray and bake in the preheated oven for 25 minutes or until cooked through. Allow to rest, wrapped, for 5 minutes before bringing to the table, slicing thickly and serving. The pork will be lovely and pink in the middle; this is perfect!