The Altar Cross

In an homile on the Holy Cross, the Priest mentioned that the practice of putting a cross on the Altar is actually a Reformational practice. I looked into it a bit and found that there is no evidence for any altar crosses before the 13th century, and even then it was not widely employed. We know that Bede's "Historia ecclesiastica gentis Anglorum" contains reference to a Processional Cross going before St. Augustine, so that is an ancient practice. And there are citations that later (13th-14th C.) the cross was taken off the pole and placed onto the altar during service. So there was the idea of having a cross on the altar, but no such thing as the Altar Cross we are familiar with. I am still looking at things, but it would seem that the Reformation popularized the practice of having an altar cross, and particularly in England (spreading from there to the continent). I thought this was an interesting bit of history, has anyone else heard anything about this, or maybe could find more info?