Here's one for Bik74.(Others may answer of course) ... Which caliph made the Christians wear wooden crosses, half a meter long by half a meter wide, around their necks?

I dont know yet. I will try & find out. But remember when you use the word caliph... it refers to the first 4 muslim rulers only (that came after Muhammed (peace be upon him)). So is the word caliph still applicable or should it be 'which muslim ruler'? Just asking so that i head in the right direction. Peace.

As i thought it not one of the first 4 caliphs.

The name is Hakim bi-Amr who was the sixth Fatimid Caliph in Egypt, ruling from 996 to 1021.

Sorry not giving the link of my source. Its Wikipedia.

Good answer Bik74.

Source