Preheat the oven to 200°C/ 400°F/Gas 6. Heat the olive oil in a pan and fry the onion until soft. Add the mushrooms and Pancetta and cook for a further 5 minutes. Remove from the heat, stir in the orange zest and juice, and the breadcrumbs. Season with black pepper and allow to cool.

Unroll the pork onto a large flat surface and spread the stuffing evenly onto the middle of the leg. Re-roll, enclosing the filling, and secure with string. Weigh the rolled joint so you can calculate the cooking time (see step 4).

Lift into a roasting tin and make small shallow slashes into the fat of the pork. Then use your hands to rub the oil into the skin, followed by the salt

Roast for 20 minutes per 450 g, plus an extra 20 minutes (it should take about 1 hour 30 minutes). Remove from the oven, cover loosely with foil and allow to rest for 20 minutes before carving. Reserve any juices for the gravy.