For almost 13 centuries, from the death of the Prophet Muhammad in 632 to the overthrow of the last Ottoman caliph in 1924, the Islamic world was ruled by a caliph. Translated from the Arabic ‘Khalifa’, the word ‘caliph’ means successor or deputy. The caliph was considered the successor to the Prophet Muhammad.

It is a term that has, at times, been abused. In June 2014, a militant group calling itself the Islamic State in Iraq and the Levant (known as ISIL or ISIS) declared the establishment of a caliphate and proclaimed its leader, Abu Bakr al-Baghdadi, a caliph. This proclamation was rejected by the overwhelming majority of the world’s Muslims.