Roast lemon and mustard pork with one-pan vegetables

Name: Roast lemon and mustard pork with one-pan vegetables
Prep time: 25 min
Cook time: 1 h 15 min
Total time: 1 h 40 min
Cuisine: Italian
Ingredients: 1 tbsp vegetable stock; 1 tsp mustard powder; Juice and zest of 1 unwaxed lemon; 900g boneless pork loin, visible fat removed; 800g floury potatoes, such as Maris Piper or King Edward, quartered; 2 medium leeks, roughly chopped; 1 medium red onion, cut into wedges; 1 medium butternut squash, peeled, deseeded and cut into 2.5cm cubes; 3 parsnips, cut into 2.5cm cubes; Low-calorie cooking spray; 2 tsp dried thyme; Handful fresh thyme leaves, roughly chopped