Pat the chicken dry with kitchen paper and remove any string before placing it in a roasting tin. Use a pestle and mortar to grind together the garlic powder, onion powder, sugar, 2 tbsp sea salt flakes and 1/2 tsp finely ground black pepper. Sliding your hands under the skin from the neck and around the breasts, carefully separate the skin from the meat of the chicken. Spread the brine all over, rubbing it underneath the skin and inside the cavity. Chill, uncovered, for at least 12 hrs, or up to 24 hrs if you have time. Remove from the fridge 1 hr before cooking, and brush off any remaining brine from the skin so it doesn’t burn. Rub the vegetable oil all over.

Heat the oven to 220C/200C fan/ gas 7. Roast the brined chicken for 15-20 mins, then baste with the juices in the pan. Reduce the heat to 180C/160C fan/gas 4 and cook for a further 1 hr-1 hr 15 mins until cooked through. The juices should run clear and a meat thermometer inserted should read 75C. Remove the chicken from the tin and rest for at least 10-15 mins before serving.