But for the record, I never said that they promised the Jews a state on the entire area west of the Jordan river. I said that they had written to Arab leaders that they had not promised them a state west of the Jordan river. These are not the same thing.
But since you brought it up, I checked, and I was slightly inaccurate. They had actually explicitly denied that they had promised the Arabs independence at all in Palestine.
Here is what Sir Henry MacMahon, High Commissioner for Egypt, wrote to the Sharif of Mecca in 1915: "I feel it my duty to state, and I do so definitely and emphatically, that it was not intended by me in giving this pledge to King Hussein to include Palestine in the area in which Arab independence was promised. I also had every reason to believe at the time that the fact that Palestine was not included in my pledge was well understood by King Hussein."
True, but you did say something very close to it:
The Palestine referred to here included all of Jordan as well as Israel and the "occupied territories". So when you say it was supposed to be "IN Palestine" not "All of" that is exactly what occured. West of the Jordan was to be the Jewish homeland, east of the Jordan an Arab state
So I will rephrase my question. Where did the British promise that the whole area west of the Jordan was supposed to be the Jewish homeland?