After World War I, the British were taking a close look at Arabia and who the future belonged to there. The Foreign Office looked to the Hashemite Dynasty in the Kingdom of Hejaz. The Hashemites had been Sharifs of the Holy Places of Mecca and Medina, and the Sharif had sided with the British against the Turkish Sultan, his master.
In addition to the Kingdom of Hejaz, junior members of the family were placed on thrones in (Trans)Jordan and Iraq.
The India Office looked to the Kingdom of Nejd and its ruler, ibn Saud. Here, the ruling family was aligned to a puritanical Islamic sect, the Wahhabis. For some reason, the India Office won the debate. Ibn Saud ousted the Hashemites from Mecca and Medina, and established the Kingdom of Saudi Arabia.
But supposing it had gone the other way, with the British Foreign Office winning the debate, and the Hashemites ousted Saud from the Nejd? What then?