The oil-fuelled rise of the Wahhabis, the austere, even puritanical (if such a word can be applied to Muslims) literalists from Saudi Arabia, has eclipsed far older Muslim traditions of independent scholarship, mysticism and even sensuality. From Pakistan to Morocco, young believers learn the Koran by heart, certain that they need enquire no further. Nowadays in Omar Khayyam’s native Iran, radical Shiite clerics run a tyrannical regime where teenagers are hanged from cranes in public for having sex.

Looking at the rage pouring out of the Muslim world, and the clash of ideas between radical Islamism and Western liberalism, it is sometimes hard to remember that several centuries ago the Islamic lands were the crucible for scientific advancement, where thinkers and scientists fused Indian arithmetic with Greek philosophy