On the eve of the November election, Mensch published a sensational story reporting that a special intelligence court in Washington had granted a warrant to allow the FBI to conduct surveillance of “US persons” in an investigation of possible contacts between Russian banks and the Trump organisation.

At the time, the story did not cause much of a ripple. It was published on Heat Street, a libertarian-leaning website run by News Corp, and an unknown quantity in journalism. So was Mensch, whose recent public profile consisted mainly of a string of angry Twitter spats.

Meanwhile, the combined investigative forces of the US media had spent months seeking to prove a secret connection between the Trump campaign and the Kremlin and had come up with very little.

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Two months later, however, the BBC put out a story echoing Mensch’s original report about the Foreign Intelligence Surveillance Act (Fisa) court warrant issued in October to allow the justice department to look into transfers and communications between the Russian banks and Trump associate – and that US intelligence agencies were investigating the link.

The Guardian separately confirmed the original request for a Fisa warrant, which had been turned down earlier in the summer, and former officials said they believed that the Mensch and BBC account of the Fisa warrants was correct.

In mid-January, the McClatchy news agency said one of its sources had also confirmed the report, and the New York Times’ public editor, Liz Spayd, published an assessment of its coverage of the Trump-Moscow link on 20 January, arguing that it had been “too timid”. The Times, Spayd argued, “knew several critical facts: the FBI had a sophisticated investigation under way on Trump’s organization, possibly including Fisa warrants”.