Remove the pork from the fridge and unwrap it. Leave it for 30 mins before you start to cook it to come to room temperature. Preheat your oven to 220°C/Fan 200°C/Gas 7.

Peel and finely chop the onion. Trim the carrots and cut them into small pieces. Peel and grate (or crush) the garlic, setting half to one side in a small bowl.

Place a medium pan on a medium heat for a min then drizzle in 1/2 tbsp olive oil. Add the onion and carrot to the pan and fry gently for 5 mins till softened slightly.

While the veg is cooking, add the wholegrain mustard to the bowl with the garlic. Add a good pinch of salt and pepper and 1 tsp olive oil. Mix well. Place the pork tenderloin onto a lined baking tray. Using the back of a spoon, spread the garlic and Dijon mix all over the pork.

Fill and boil the kettle. When the carrots and onion have cooked for 5 mins, add the reserved garlic to the pan and fry for 1 min, stirring. Tip in the lentils and stir. Pour in 400ml hot water from the kettle and crumble in the stock cube. Pop a lid on the pan and simmer for 15 mins.

As soon as you have put the lid on the lentils, slide the pork into the hot oven and roast for 15 mins. After this time it should be cooked trough, there should be no pink. Check by piercing the fillet with a sharp knife. The juices should run clear. Cook a little longer till they do.

Remove the pork from the oven and set to one side to rest. Taste the lentils. They should be tender. Add more slat or pepper if you think they need it. Stir through the baby leaf spinach to slightly wilt it. Cut the pork into thick slices and serve on top of the spinachy braised lentils.