“QUEEN ELIZABETH must claim her right to rule Muslims.” So ran a recent headline on the Arab Atheist Network, a web forum. It was only partly in jest. According to reports from Casablanca to Karachi, the British monarch is descended from the Prophet Muhammad, making her a cousin of the kings of Morocco and Jordan, not to mention of Ayatollah Ali Khamenei, Iran’s Supreme Leader.

The claim, first made many years ago, is gathering renewed interest in the Middle East. Why is not clear, but in March a Moroccan newspaper called Al-Ousboue traced the queen’s lineage back 43 generations. Her bloodline runs through the Earl of Cambridge, in the 14th century, across medieval Muslim Spain, to Fatima, the Prophet’s daughter. Her link to Muhammad has previously been verified by Ali Gomaa, the former grand mufti of Egypt, and Burke’s Peerage, a British authority on royal pedigrees.

Much hinges on a Muslim princess called Zaida, who fled a Berber assault on her home town of Seville in the 11th century and wound up in the Christian court of Alfonso VI of Castille. She changed her name to Isabella, converted to Christianity and bore Alfonso a son, Sancho, one of whose descendants later married the Earl of Cambridge. But Zaida’s own origins are debatable. Some make her the daughter of Muatamid bin Abbad, a wine-drinking caliph descended from the Prophet. Others say she married into his family.

Reaction to the queen’s purported Muslim extraction has been varied in the Arab world. Some have warned of a perfidious plot to revive the British empire with help from Muslims, particularly Shias, who revere the Prophet’s descendants. They note that the BBC’s Arabic channel ran the bloodline story. But others welcome the news. “It builds a bridge between our two religions and kingdoms,” says Abdelhamid Al-Aouni, who wrote the article in Al-Ousboue. Other reports have called the queen sayyida or sherifa, titles reserved for the Prophet’s descendants.

Her son, Prince Charles (bin Philip), is intrigued by Islam. “Perhaps there were times when he wanted to marry more than one wife,” says one of his Muslim confidants. Charles is a patron of the Oxford Centre for Islamic Studies, where he greets audiences with the Muslim salutation, as-salamu alaykum (peace be upon you). He is said to want a multi-faith coronation and to be ordained as “defender of faith”, not “the [Christian] faith”. He might try amir al-mumineen (commander of the faithful), an honorific favoured by Muslim rulers.