Thanks. The Holy Grail is in that church in Ethiopia?
Now the Chalice theory is to be distinguished from the author's objective.
This lady is correct--there must have been a stone goblet used at the Last Supper so if you found it, it would be another artifact confirming the Scriptural account.
But, Graham Hancock's analysis (in "The Sign and the Seal") is that the author's use of the Grail as well as subsequent Grail stories are developed from a knowledge in the region that the Knights Templer had located the Ark of the Covenant; the literature is intended to leave a description of the the location of the Ark in Ethopia.
That's the Ark of the Covenant the Ethiopians used to beat the Italian army in nineteen ought something.