Former FBI director James Comey at his home in Virginia. Credit:AP On the same day, The Washington Post concluded: "We have said for months that that investigation - into Russian meddling in the US election - must be a priority for both the executive and legislative branches. We need to know what the Russians did and take steps to prevent a recurrence. "To that urgent inquiry now must be added an investigation into the events and disclosures of this week [on the Comey sacking]. Congress and the American people must hear from Mr Comey and [Deputy Attorney-General Rod] Rosenstein, and Congress must ensure that the Russia investigations proceed, unfettered." On Thursday, Trump ended days of buck-passing when he claimed personal responsibility for dumping Comey – and spelled out his self-serving reason. In an interview with NBC's Lester Holt, Mr Trump said: "When I decided to just do it, I said to myself, I said, you know, this Russia thing with Trump and Russia is a made-up story." But there is too much evidence already on the public record for such a peremptory dismissal, or for the use of such formulas as "fake news" and "witch hunt".

The termination letter from US President Donald Trump to FBI director James Comey. Credit:AP Let's be clear here - so far there is no smoking gun. But given the mountain of evidence and Trump's constant squirming at the notion that he and/or his campaign and his associates might be investigated, he is the last person who should act to thwart any investigation. After a week that ended with a massive, global cyber attack on computers in more than 100 countries, it's worth remembering that "this Russia thing" started with two demonstrably true aspects of the 2016 campaign - Trump's obsequious courting of Russian President Vladimir Putin and the hacking of the Democratic Party campaign's computers, which the combined US intelligence services concluded was a bid by Moscow to give Trump a leg-up over his rival Hillary Clinton. Deputy Attorney-General Rod Rosenstein is at the centre of the storm over James Comey's sacking. Credit:Bloomberg Democrats and even some Republicans insist that the core question of Russia's election meddling must be investigated – as a result of which, up to half-a-dozen congressional committees, all mired to varying degrees in partisan bickering, are running probes in parallel with the FBI investigation.

And that is the backdrop against which insiders, political and institutional, have fuelled relentless reporting on the questionable conduct of Trump, his aides, his campaign team and his associates. Donald Trump's inability to focus his attention makes it hard for him to learn and master facts. Credit:Bloomberg Sensationally, Trump was forced to let go of retired US Army general Michael Flynn in February, for his dealings with Moscow as the Obama administration was imposing sanctions on Russia in retaliation for the election hacking. Now Flynn is under investigation for accepting tens of thousands of dollars from Moscow in 2015. Yet when Flynn, Trump's national security adviser, was proved to have lied about his communications with Russian ambassador Sergey Kislyak, thereby exposing himself to possible blackmail by Russia, it was weeks before Trump took any action. Then FBI director James Comey testifies on Capitol Hill earlier this month. Credit:AP

Acting FBI director Andrew McCabe waits to begin a Senate Intelligence Committee hearing on May 11. Credit:Bloomberg James Clapper, director of national intelligence for Obama, denied Trump's wiretap claim. And asked about Trump ties to Russia, he didn't mince his words: "We had no evidence of such collusion." But in March, Comey disclosed that as early as July 2016, the FBI had begun an investigation of the Russian election interference and "any links between individuals associated with the Trump campaign and the Russian government". Lost in the fracas is the message that Trump's political assassination of Comey sends to the FBI director's hapless successor: persist with the investigation of "this Russia thing" at your peril. Loading

The President's signalling is a so-called red line – facts be damned, Trump is demanding that the investigation be wrapped up quickly and that his campaign be exonerated of charges that it colluded, or was complicit in, Moscow's meddling in the 2016 election. Maybe it should be exonerated. But by sacking Comey, Trump has made it very likely that Americans, and the world, will never know for sure – and that the FBI's rank and file will do all it can to make it impossible for any Trump appointee to shut them down.