Abd al-Rahman I was the founder of the Umayyad dynasty in Hispania, and he was one of the last Umayyad survivors when the Abbasid overthrew the Umayyad caliphate in Damascus. According to what I read, he fled Damascus, travelled west on low profile, and finally arrived in Hispania after 6 years missing. In Hispania he quickly amassed support, defeated the local Muslim ruler and installed himself as Emir. According to Wikipedia:
Abd-ar-Rahman I became Emir of Córdoba in 756; fleeing for six years after the Umayyads had lost the position of Caliph held in Damascus in 750. Intent on regaining a position of power, he defeated the existing Islamic rulers of the area who defied Umayyad rule and united various local fiefdoms into an emirate.
I'm curious how the people in Hispania verified that he was in fact Abd al-Rahman, the Umayyad prince, because:
He travelled on low profile, so I guess this also mean without strong troops or obvious indicator of being a royal
Hispania was pretty far from Damascus, so probably Hispanic peoples have less idea about how Umayyad princes look or how to verify them
He didn't seem to be an important prince, like the heir to the throne, he just happened to be one of the survivor.
Yet enough people in Hispania believed him to allow him to take over.