Mix the two mustards, honey and half of the minced garlic.
Rub the pork loin with most of this mixture and marinate for minimum 30 minutes, up to 2 hours.
Meanwhile, put the potatoes in a pan of cold water. Bring to the boil and cook for ten minutes, then drain and let them cool.
When cooled, cut them in half.
Preheat the oven to 180°C.
Heat half of the oil in a frying pan and sear the meat all over for a few minutes, them move it to a large baking tray. If the loin is too big, cut it in half before frying.
Arrange the potatoes around the pork, then scatter the thyme leaves and minced garlic over the potatoes, then brush them with the remaining mustard sauce, using a silicon brush.
Drizzle with olive oil, season with black pepper and salt, if required (the mustard is salty, so be careful with the salt).
Roast in the oven for about 30 minutes, or until the potatoes are crispy and the pork has cooked through.
Serve warm.