To Corbyn's dismay, the story of the US-UK dossier has mostly been its origin

As Jeremy Corbyn took to the stage on a Wednesday in November brandishing secret documents 15 days out from the 2019 election campaign, it was potentially the Hail Mary moment to salvage the Labour leader’s campaign. Labour had discovered the explosives that would blow up Johnson’s seemingly bomb-proof three-word election campaign: “Get Brexit Done.”

The documents Corbyn held up to the cameras brought together two of Labour’s most deadly attack lines: Brexit meant desperate free trade deals with the avaricious Americans, and the UK trade negotiators were secretly preparing to expose the NHS to the chill wind of the US private pharmaceutical industry. The beloved NHS was about to be sold to Donald Trump’s friends.

Surrounded by smiling junior doctors, Corbyn said the 451 pages of unredacted documents “leave Boris Johnson’s denials in tatters and showed our NHS is already on the table for a toxic deal”. The documents covered six rounds of talks from July 2017 to “just a few months ago”.

A flustered Conservative party tried to kill the sense of drama by saying the documents had already been available online for two months, and were simply a read out of working group meetings between officials. It later emerged the Telegraph may have seen the documents as the basis for a story back in July.

The consensus was that papers had indeed been lying fallow on the social news site Reddit, unexploited by any reporter or politician.

But within days of his dramatic press conference, the media – prompted by the Tories – were questioning the origins of the documents, and suggested they might have been put on to Reddit by Russian hackers.

Labour’s Laura Piddock, one of Corbyn’s closest allies, thrown on the defensive, said it was a massive distraction to claim the authors were Russian. The document was an authentic British government paper. But by then Labour’s explosives had been made safe. The story was the origin of the document, and not its content.

With days to polling day, the Sunday Times reported British spies had found the documents had been circulated on Reddit, three German-language websites and a Twitter account. They had a similar dissemination pattern – including grammatical errors – used by Secondary Infektion, a Russian operation exposed by Facebook.

Reddit itself said it had banned 61 accounts linked to the release of the documents because it believed the leak was “part of a campaign that has been reported as originating from Russia”.

There was no suggestion that Labour had acquired the documents illegally, although it could be argued the party did not advertise the fact that the documents had not been handed directly by a whistleblower.

Last month on the eve of the publication of the much delayed intelligence and security committee report into Russian meddling into British democracy, the foreign secretary, Dominic Raab, formally confirmed the Reddit papers were part of a Russian hackers dump, and said there had been Russian effort to amplify the information’s existence, presumably through twitter.

Now the near-final piece of the jigsaw has fallen into place. The documents were hacked from the office of the former trade secretary Liam Fox.

Doubtless Corbyn will be criticised for being Russia’s useful but ineffective idiot, but it’s unlikely any politician in the moral maze of an election campaign will be so scrupulous as to spurn a chance to publicise an authentic and damaging document simply due to its murky origins.