Because turkey breast meat is so lean, you need to protect it from drying out during cooking. There are different ways of doing this. The simplest are using steam.

Steaming Your Turkey

 
 
REMEMBER: 
Ensure your turkey is completely defrosted before cooking
 
 Method:
Place a rack in the bottom of your roasting pan. Pour water into the pan up to the level of the rack so that the turkey is held above the liquid and is less likely to “stew” on the base.
Place turkey (defrosted; minus neck, gizzard, heart and liver, and knobby ends of drumsticks) in the pan.
The water will create a steamy atmosphere that keeps the flesh moist.
Cook for at 180°C for a total cooking time of 15 minutes per 500g plus an extra 15 minutes. (A 5 kg turkey takes approximately 2¾ hours. A 5 ½ kg turkey takes approximately 3 hours.)
 
NB/ Try using flavoured liquids instead of water e.g turkey or chicken stock mixed with wine or fruit juice and herbs.
How to know when your turkey is cooked: 
If your Crozier turkey has a pop-up timer inserted in the breast, it will pop up when it reaches the temperature of 85°C.
Or, if you pierce the thickest part of the turkey thigh with a skewer, juices will run out. If the juices run clear the turkey is cooked. If there is still some pinkness (blood) present, longer cooking is required.
Use flavoured liquids instead of water e.g turkey or chicken stock mixed with wine or fruit juice and herbs.  In addition to the skewer test, give the drumstick a wiggle The leg should move freely when cooked, with little resistance.
NB/ Younger turkeys (and chickens) have underdeveloped porous bones, which may allow red pigmentation (haemoglobin) to run into the meat. If the bird is fully cooked (80°C and the thigh juices run clear) the meat is safe to eat even if there is some pink colouring in the flesh surrounding the bones.
After removing your delicious cooked turkey from the oven, lift it from the roasting pan to a carving platter or board and lightly cover it with foil. Allow it to rest for about 10 minutes while you prepare the gravy. Resting allows time for the flesh to relax and for juices to be reabsorbed into the meat before carving.