1.   Compiling and using a press list Many organizations have press lists, which they keep as closely guarded secrets.

2.   He knew that the routine and itinerary of the Chairman were a closely guarded secret.

3.   The companies that administer the warehouses keep details of their contents a closely guarded secret.

4.   The details of her death have stayed a closely guarded secret.

5.   The details of his death remain a closely guarded secret.

6.   The level of Marks required for entrance to secondary school is a very closely guarded secret and seldom officially revealed.

7.   The recipe is a closely guarded secret.

8.   Today the locations of many rare or endangered species are closely guarded secrets.

9.   Her whereabouts are a tightly guarded secret.

10.   Ever wondered why the formula for Coca-Cola is such a closely guarded secret?