Place the pork loin on a tray and season well with salt and pepper. Add the mustard and olive oil. Rub all of the mustard into the pork. Leave the pork covered at room temp for at least 20 minutes to get the temperature up before cooking.
Preheat the oven to 150°C.
Place a large heavy based pan on a medium heat. Once the pan is warm add some oil and then the pork. You’re looking for a gentle sizzle to caramelise the mustard. If it’s too hot turn it down or if it’s not frying gently crank the heat up a bit.
Fry the loin for around five minutes. Turn and repeat. Lightly sear the sides of the loin. Add more oil if needed but not too much. Place the seared loin onto a roasting rack and into the oven.
Cook for around 20 minutes but if you have a thermometer test the internal temperature. We are looking for 55°C. If you don’t have a thermometer to test the temperature, check by pressing the loin. The pork should have a little resistance and bounce back when pressed. Once cooked leave to rest on the bench for around 15 minutes and then refrigerate.
To make the dressing, combine all the ingredients in a bowl and whisk together. Add more olive oil if it seems too thick to drizzle over the pork. Check for seasoning, the salt should be fine due to the capers and anchovies.
To serve, thinly slice the pork. Lay the slices in a circle close to the edge of the plate and continue inwards to cover the plate, as a carpaccio might be served. Season the pork with a little salt. Generously dress the pork. Add some radishes and salad leaves. Spoon some dressing over the radish and salad. All the dressing may not be needed but I like a lot on this dish.