In the early 1920's the power balance in Arabia changed. Sultan Abdul Aziz ibn Saud of Nejd was expanding his realm in all directions and defeated longstanding enemies. Ibn Saud was supported to a certain degree by Great Britain, but one of his main rivals, Hussein b. Ali, Sharif of Mecca and King of the Hejaz, was also supported by the British. A former British Agent once said that "ours is a Hussein policy" and there was no doubt that Britain focused most of their energy on Hussein. Britain's ideas on Arabia, however, slowly changed as Ibn Saud grew more and more powerful and as Britain found Hussein more as a burden than a valuable ally. The same Agent, Col. Vickery, spoke of this growing power in November 1922:
I see also in Arabia, a growing power, a power not of our forging, a power which will eventually overrun the very homes of these we have so openly and so prodigally supported ... The custodianship of the holy places lies now with the Sharif of Arabia [sic], but I feel that peace will not descend on Islam till the cities of the Prophet are once again under the aegis of a Mohamadan nation which unites both spiritual and temporal power.
Three years later the Hejaz fell to Ibn Saud's fanatic fighting force, the Ikhwan, and thereby ending Hashemite rule over the holy cities of Islam. Hussein fled to Aqaba and was then "invited" by the British to Cyprus.
(The quote is from Randall Baker's book King Husain and the Kingdom of Hejaz.)