I no longer believe that Marion Aten is an ace. Norman Franks, in
Above the Trenches, based his five victories, as far as I know, on Last Train, although he references Jackson's book on the Allied intervention in Russia, which in turn is based on Last Train.
On my last visit to the PRO I found the ORB for 47 Squadron in South Russia. It states, on August 19, 1919, that Aten had just arrived from London. Since Last Train, Jackson, and then Franks, have his five victories as occurring in the April/May 1919 period, I do not see how they can be considered other than fictional.
He died May 10, 1961.
Frank.