Historians believe the Queen is a descendant to the founder of Islam - after tracing her family tree back 43 generations.
The claim would make the British monarch a distant ancestor of the Prophet Muhammad.
The findings were first published in 1986 by Burke's Peerage, a British authority on royal pedigrees.
But the claim has recently resurfaced after a Moroccan newspaper said it had traced the queen's lineage back to the Prophet.
According to their findings, Elizabeth II's bloodline runs through the Earl of Cambridge in the 14th century, across medieval Muslim Spain, to Fatima, the Prophet's daughter.
Although disputed by some historians, genealogical records of early-medieval Spain also support the claim and it has also been verified by Ali Gomaa, the former grand mufti of Egypt.
Burke's publishing director wrote to the-then Prime Minster Margaret Thatcher in 1986 calling for increased security for the royal family.
'The royal family's direct descent from the prophet Mohammed cannot be relied upon to protect the royal family forever from Moslem terrorists,' he wrote to Thatcher.
Recognising the connection would be a surprise to many, he added, 'It is little known by the British people that the blood of Mohammed flows in the veins of the queen. However, all Moslem religious leaders are proud of this fact.'
