It was one of Hatto's recordings of Liszt that Gramophone magazine writer Jed Distler popped into his computer in early February, and iTunes loyally searched the Gracenote database for a match. Found one, too -- but not to a Hatto CD; the disc matched another Liszt recording by pianist László Simon. When Distler pulled that CD from his collection and played it alongside the Hatto disc, they sounded precisely the same.
The ensuing cascade of suspicion, comparison, testing and confirmation is documented thoroughly in the Gramophone and Stereophile articles (and explicated further in the Pristine Audio and CHARM analysis pages), but the summary version: most if not all of Hatto's late recordings are apparently copied from other artists, some modified to hide the theft, some just duplicated as-is. If not for the surprise iTunes ID, this might have gone undetected for much longer. I've often seen iTunes and Gracenote make wildly inaccurate guesses when confronted with rare or custom CDs, but in this case I suppose that wild guess was forensically sound.