==Great Church== 
 I agree that there was one "great church" before the 12th or whatever century. But I find the phrase "Great Church Orthodox and Catholic" confusing. I have never heard the phrase "great church" before. Since it preceded the term "Orthodox", I thought it was some appellation  unique to them. My suggestion would be something that calls the church "Christian" which can be understood by anyone, followed by a phrase that links the two divisions of the Christian church at the time. So I guess I did understand the phrase eventually and tried to change it. If you could modify the phrase to something that is clearer, I would appreciate it.