It is surely a matter of the gravest concern if, as the latest Russian evidence suggests, MI6 was responsible for the forging of a document intended to discredit a prime minister and influence the result of a general election.
Whether the present Foreign Office inquiry will actually get at the truth is, however, another matter. The Foreign Secretary has already said that the MI6 files for the relevant period are "incomplete" and "offer an inconclusive picture on whether the Zinoviev Letter was a forgery". There is another relevant class of documentation which I suspect will turn out to be in a similar state.
As the FO report's author, Gill Bennett, has indicated, the really interesting aspect of the affair is how the Zinoviev Letter came to be leaked to the Daily Mail. The prime suspect for the leak is in fact the head of MI5's (b) branch, Joseph Ball, who went on to become the original spin-doctor and dirty-trickster at Tory Central Office. Last year's much-hyped release of early MI5 records provided ample evidence of an archival scorched-earth policy on the part of MI6's sister service; MI5 documentation regarding the inter-war period (which is apparently due for release this year or next) will doubtless have received the same treatment.
Won't it be ironic if Ms Bennett finds more glasnost in the KGB archives than in those of our own spooks?