Preheat the oven to 200°C, fan 180°C, gas 6. Put the orange zest, thyme leaves, garlic and olive oil in a pestle and mortar and crush together to make a marinade – or use a bowl and the end of a rolling pin.
Rub the marinade all over the turkey and put the crown in a roasting tin. Season with black pepper and cover loosely with foil.
Cook in the oven for 20 minutes per kg, plus 70 mins, removing the foil after 1 hour and drizzling over the orange juice. To test if the turkey is cooked, pierce the thickest part with a skewer. The juices should run clear. If not, continue to cook. When done, remove the turkey from the oven, cover with foil and rest for 15-20 minutes before carving.