The furore began with claims by a ex-spy, who worked for the former Czechoslovakia during the 1980s, that he had met Mr Corbyn, that the then backbench Labour MP knew he was an agent and had supplied information nonetheless.
While some meetings did take place, Mr Corbyn denies knowing Jan Sarkocy was a spy, an assertion backed by the official Czech archives.
Mr Sarkocy’s account is also undermined by a bizarre claim to have organised the Live Aid charity concert, which he said was paid for by Czechoslovakia.
However, the affair has shed fresh light on the existence of a file on the Labour leader kept by East Germany’s Stasi.
Such files can be publicly revealed, but only with permission of the person it was about.
Mr Corbyn needs to do this, even though the document may contain inaccurate information, given spies’ propensity to exaggerate their successes.
If he does not, the story will follow him until the next general election and could play a decisive role.