Sit the turkey in a large roasting tin, breast-side up, and gently push your fingers under the skin until you can fit your whole hand down the length. Season the turkey all over with 1 tbsp sea salt flakes. Cover and chill for at least 1 hr, or up to 24 hrs.

Remove the turkey from the fridge 1 hr before cooking so it can come to room temperature. Beat the butter, orange zest and half the rosemary leaves with some pepper. Transfer the turkey to a board and put the onions, carrots and turkey neck and giblets into the tin. Sit the turkey on top, then spread about 4 tbsp of the flavoured butter under the skin, over the breasts, using your hands. Spread the rest of the butter over the outside of the turkey, ensuring the legs and wings are well coated. Put the orange halves and rosemary stalks in the cavity.

Heat the oven to 180C/160C fan/gas 4. Work out the cooking time based on 40 mins per kg. A turkey this size will need about 2 hrs 40 mins, plus 30-45 mins resting. Cover the turkey loosely with foil and roast for 2 hrs. Remove the foil and brush generously with some of the marmalade, then roast for 15 mins more. Brush with more marmalade and sprinkle with the remaining rosemary leaves. Return to the oven for a final 15 mins. Check the turkey is cooked through by inserting a meat thermometer into the thickest part of the breast – it should read 65C, and the thickest part of the thigh should read 75C. If the turkey isn’t up to temperature, return to the oven for 15 mins at a time until it’s cooked through. Leave the turkey in the tin for 10 mins, then lift onto a lipped board or tray to rest, uncovered, for at least 20 mins, or up to 40 mins.

To make the gravy, skim all but about 2 tbsp fat off the juices in the tin. If the roasting tin is flameproof, put it directly over a medium heat. If not, tip the juices into a large shallow pan first. Scatter over the flour and stir to make a paste, then stir in the wine and bubble for 2 mins. Pour in the stock and bring to a simmer, then add the soy sauce and simmer for 10 mins until the gravy has thickened. Add any resting juices from the turkey to the gravy, season to taste, then strain into a jug. Carve the turkey and serve with the gravy on the side.