Dear JDS1949,
firstly, thank you for your interest and time in attempting to unravel this mystery:
The AE Harrison you found who was attached the Bed's and Hert's Reg and the 4th Norf Reg is Alfred Ernest Harrison, I have spent some time on this fellow previously and have quite a lot of info on him in addition to his Service Record. Interestingly there was at one point some concern that his name was actually AE Harris and not Harrison at one stage, another reason to suspect his authenticity.
However further research revealed an impeccable history with significant personal references, and family connections consistent with a ridgy-didge British AE Harrison, I have attached a page from his service record, could you please confirm this is the man you found
The non listing of Temporary Officers in the Gradation list is both good and bad, not having them in the list is a serious shortcoming, but the fact that have this knowledge is better than being misled by the false understanding that he should be in the list and isn't.
In relation to the conversation with the NA expert and her subsequent suggestions, I tend to agree that we are amidst a research process that has covered most of the obvious possibilities, that are either logical or consistent with accepted procedures and methods.
However, this doesn't account for the possibility of information DISTORTION !!!!
I had made an informal approach to the MOD a couple of weeks ago, they haven't got back to me yet, and I didn't expect an answer any time soon. I know of the requirements made of record requestors and these are quite onerous particularly if you are unable to provide such things as the unit or regiment or other relevant particulars. I'll now make a formal enquirery complete with all the unsuccessful background research to date and his personal and AIF military records.
I'm not all that confident about a successful outcome at the MOD. Contemporary privacy rules are good for us all and are usually applied equally across the board for good reason in most circumstances. On this occasion, I would like to inspect quite a few records assuming there might be several men of interest as in the NA records. Never the less, I will ask?!!
It is interesting that you mention that as a result of the limitations of the Gradation Lists not having Temporary Officers listed, that we now know that there were no Permanent Officers with the name AEH commissioned between August 1917 and 1920.
I would love to be 100% sure of any resource, I am beginning to believe that there are so many aberrations in these records, files and indexes that there is some doubt in my mind as to their accuracy. Notwithstanding that we are lucky to heve them at all!! I make the example of the A E Harrison listed in the WO338 written index, extracted and posted here two weeks ago, this is a long number (210475) in the WO338 series and when you go to that record it doesn't exist?

Interestingly this Albert Edward Harrison has his unit smudged out by an ink blot, Alfred Ernest Harrison is the next entry of 218661
A couple of questions:
I understood that Temporary Officers had their commissions withdrawn when the war finished in 1918, Why would a Temporary Officer go on after the war had finished and his records be located in the yet unreleased records at the MOD. Weren’t Temporary Commissions only operational during the War?
If there were no AEH permanent Officers Commissioned in the Gradation list up until 1920 then logically why and how would his records be in the unreleased MOD files. As usual I could be missing something here?.....LOL
As you say, maybe some future luck in the Army lists 1920-1924
I have attached two documents, the one I attached a couple of weeks ago the W)338 index describing A E Harrison long number 210475 with the ink smudge and also Alfred Ernest Harrison 218661 and also Alfred Ernest Harrison's Commission application document for confirmation
Interestingly, with Alfred Ernest Harrison he is given a Temporary Commission in February 1920 after the War has ended, and his records are with the National Archives, how does this work?
Many thanks
Ian