Norman Foster and Zaha Hadid, two respected and influential British architects, are among those who have apparently been approached to take on the project by King Abdullah, Saudi Arabia’s monarch whose list of titles also includes “custodian of the two holy mosques”. Their involvement has raised hackles in Saudi Arabia.

Lord Foster may have won the prestigious Pritzker architecture prize but he is not a Muslim. The idea of a non-Muslim redesigning one of the world’s most important mosques has provoked deep unease in Saudi Arabia. And as only Muslims are permitted to enter Islam’s holiest city, were he to win the commission, Lord Foster would have the tricky task of seeing through his design from a distance.