Preheat oven to 180 C / 160 fan / 350 F.
Check the cavity for giblets. If they are there, remove. Option to put in the roasting tray (minus the bag) for tasty gravy.
Add the onion, carrot, celery and garlic to your tray plus water.
Add the herbs to the cavity but leave enough space for air to circulate.
Rub olive oil all over the turkey and into the nooks and crannies. Sprinkle the top and bottom with salt and pepper. Place the turkey on top of the trivet (upside down for the juiciest bird) and cover with tin foil.
Cook a high welfare bird for 25 - 30 mins per kilo, standard 35 - 40 mins per kilo. Mine was 5.6kg and took about 3hrs 10 mins.
If cooking upside down, cook for 1 hour and then turn the right way (breast up) and cover with foil again.
About 1 hour before the end of cooking, remove the foil and baste the turkey with the pan juices. 15 - 20 minutes before the end of cooking add the parma ham.
To check it’s done, pierce into the thick part of the turkey breast or thigh with a knife or skewer. If the juices run clear, it's done.
Lift the turkey from the trivet using a big carving fork. Cover the turkey with a clean tea towel or foil and rest for around 1 hr before carving.