English: The Caliph of Tetuán, Mulay Hassan el Mehdi, arriving at Atocha Station (Madrid) in 1942.
Mulay Hassan was the second and last caliph of Tetuan and of the Spanish Protectorate of Morocco, reigning from 1925 to the end of the protectorate in 1956. Son of the first caliph Mohammed el Mehdi, he was the nephew of the Sultan of Morocco Mulay Yussuf (died 1927) and cousin of his successor, Mohammed ben Yussuf. The caliph of Tetuán was the delegate of the sultan in the Spanish Protectorate. The caliph's powers were limited and mostly ceremonial since effective power was exercised by the Spanish high commissioner, who likewise resided in Tetuán.