A turkey crown is on the bone, it is a whole turkey, that in essence, has had its legs (thigh and drumsticks) removed, though still giving the appearance of a complete bird in its silhouette. A turkey crown will provide you with a breast saddle (two whole breast lobes).
Here is a good idea for Turkey Crown cooking times.
The temperature of your oven should be 190C/170C fan/gas 5 and the cooking time calculated as follows:
Under 4kg: 20 mins per kg plus 70 mins
Over 4kg: 20 mins per kg plus 90 mins
Remember to weigh your turkey with any stuffing that is under the skin or bacon (or any other additions) wrapped around it. Finally, check that it is cooked properly.
1.5kg: 1 hr 40 mins plus resting at 190C/170C fan/gas 5
2kg: 1 hr 50 mins plus resting at 190C/170C fan/gas 5
2.5kg: 2 hrs plus resting at 190C/170C fan/gas 5
However, many turkey recipes specify a different oven temperature and if you cook the crown at a higher (see below) or lower temperature as specified by the recipe you are following, you will have to adjust the time.
For example, at 200C/180C fan/gas 6, calculate the cooking at 20 mins per 450g.
You may also have to adjust the time for the type of crown you have bought, a 3k turkey crown, for example, is cooked for 1 hr 30 mins at 180C/160C fan/gas 4, by which point the internal temperature should be 60C (5 degrees less than recommended, but perfectly safe with a KellyBronze). It will then rise a further 5C as it rests.