In July 2013, Wahhabism was identified by the European Parliament in Strasbourg as the main source of global terrorism.

Wahhabism has become increasingly influential, partly because of Saudi money and partly because of Saudi Arabia's central influence as protector of Mecca.

The Grand Mufti of Saudi Arabia, condemned Islamic State of Iraq and the Levant (Isil), insisting “the ideas of extremism, radicalism and terrorism do not belong to Islam in any way”.

Somewhat paradoxically, however, members of the Saudi ruling class have applauded Wahhabism it for its Salafi piety - i.e. its adherence to the original practices of Islam - and the movement's vehement opposition to the Shia branch of Islam.

In the 1970s, with the help of funding from petroleum exports and other factors, Saudi charities started funding Wahhabi schools (madrassas) and mosques across the globe and the movement underwent "explosive growth".

The US State Department has estimated that over the past four decades Riyadh has invested more than $10bn (£6bn) into charitable foundations in an attempt to replace mainstream Sunni Islam with the harsh intolerance of its Wahhabism. EU intelligence experts estimate that 15 to 20 per cent of this has been diverted to al-Qaida and other violent jihadists.