The question is inspired by reading The Iron Cage by Rashid Khalidi. While the book provides many interesting insights, its arguments/findings essentially hinge on the claim that the British empire was staunchly committed to Zionism and creation of a Jewish state in Palestine. Khalidi does little to justify this claim, beyond the following passages:
However, there were deep struc- tural factors of support for Zionism in Britain and for Israel in the United States that remained unchanged in spite of these measures, and that in the end prevented either of them from having any significant eƒect. An examination of how Britain’s handling of the Palestine issue helped to make it highly unpopular in the Middle East might shed light on a similar process that appears to be un- folding with regard to the United States.
and
Nevertheless, despite the fact that in the first part of the twentieth century Jews were a tiny minority of the population of Palestine, and the Zionist movement was as yet probably unrepresentative of mainstream Jewish opinion, Britain and the dominant institution of the international community, the League of Nations, were broadly faithful to that commitment. The reasons for this stand had primarily to do with the utility of Zionism to British imperial purposes, the sympathy of a major sector of the British elite for Zionism, and the skill of the Zionist leadership in cultivating those who might be of use to them.
(emphasis is mine)
It is hard to imagine that the British politicians, hardened in handling many colonies, acted merely out of sympathy for the Jews (even though some where definitely convinced Zionist supporters.) As for the utility of Zionism to British imperial purposes - I imagine that playing Zionists against the local Arab population could fit the bill just in the same way as playing against each other various Arab groups (Khalidi discusses the latter at length, but says nothing of the former.)
Were there other political reasons for supporting the Zionism?
Remark: I am not asking here for the reasons that led to issuing the Balfour declaration - these are well-known, as discussed, e.g., by Walter Laqueur's A history of Zionism, and not unlike those behind the simultaneous conflicting promises given to the Arabs (aka McMahon-Hussein correspondence) and French (aka Sykes-Picot agreement.) I am mostly interested in (alleged by Khalidi) continuous support over most of the pre-war Mandate period, i.e. from 1918 to 1939 (the year of issuing the White Paper that restricted the Jewish emigration.)