The new American president, Donald Trump, celebrated his first day in office with a barefaced lie. He said that his inauguration crowd was bigger than Barack Obama’s. As lies go it was no big deal, but it was still a lie. Within minutes, camera technology and social media had reduced Trump’s boast to ruins. His supporters briefly resorted to “alternative facts”, but rarely can a president’s opening statement to the world have been so instantly proved false.

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Two days later the British prime minister, Theresa May, came within an inch of a more serious lie, about the failure of a nuclear missile test and whether she knew of it. May refused four times on television to admit that last June’s missile test was a fiasco and that she knew anything about it.

Within hours a frenzy of electronic communication extorted a confession from Downing Street that May had indeed known but not wanted to say. When her defence secretary, Michael Fallon, stood up to repeat that the missile test was a success, it took just seconds for MPs’ mobiles to buzz with responses from the US that made Fallon look a fool.

It is clearly serious when an American president cannot tell the truth, and a British prime minister cannot come clean on defence. What is good is that their lies and obfuscation can be so swiftly exposed.

Of all golden-age fallacies, none is dafter than that there was a time when politicians purveyed unvarnished truth. As Private Eye’s Ian Hislop said in his recent Orwell lecture, suppressing truth and suggesting falsehood have been leitmotifs of politics since time began. Leaders of all sorts have used censorship to grind some personal axe, to deny George Orwell’s core principle of free speech, “the right to tell people what they do not want to hear”.

Falsity, whether about the past or the future, is the raw material from which politicians seek to fashion their personal narratives. In Nineteen Eighty-Four Orwell’s commanders used the lie as power projection, ordaining that “war is peace, freedom is slavery and ignorance is strength”. The veteran reporter Louis Heren would ask himself before being offered any confidential information by a politician, “Why is this lying bastard lying to me?”

In his study of political hypocrisy, David Runciman even exalted the role of the white lie in keeping the wheels of progress turning. Democratic government is an edifice of false promises and unrealisable dreams. It is said that Benjamin Disraeli was more attractive for having no principles than William Gladstone for having them and betraying them. Likewise, Trump is reportedly popular in some quarters for his personal failings, even mendacities, rather than for any perceived virtues. Voters seem to identify with the evil in a man more easily than with the good.

The difference now is that the lies can certainly be more swiftly spread, but also more swiftly exposed. The old maxim held that “a lie can be halfway round the world while the truth is putting on its shoes”. What is different is that those shoes are no longer needed. A political lie is no longer sanctified by office and received as wisdom from on high. It is just news, sent racing round the globe and pursued by an instant cloud of reactive clutter. How does that work? Each item of BBC news now comes broadcast with a clunking built-in rebuttal, their notion of balance. But truth then asks, what did that lying bastard say? Get after him.

When the evidence for fake news during the presidential election campaign broke cover, the reaction was intriguing. A bizarre coalition of Californian nerds, Macedonian teenagers, Russian leakers and American spies emerged to engage in an immediate digital postmortem. From this global seminar one thing emerged. The Russians were clearly lying, and so was Trump. We know something like the truth.

Trump’s lies are the product of a mind apparently unable to recognise the border between fact and fantasy

Most people now get their news about the world around them pre-digested and customised by social media. They do not get the breadth of information supplied by an even moderately impartial news source. Material is allotted them not by whether it is true but by whether they might like it. It is institutionally biased, and more vulnerable to the dissemination of lies.

But something will surely be done about this. Facebook’s claim that it was not a publisher but a distributor – a sewer, not the sewage – was as absurd as a newspaper or a broadcaster making a similar claim. It was indeed denied by Facebook’s immediate response, to shuffle its “editors” and change its algorithms. If these media oligarchs do not check their own material and introduce some form of editorial balance – gargantuan as the task must be – the mother of all lawsuits and the father of all regulators will descend on them. That is what happened with the equally chaotic rise of sensationalist “yellow journalism” in the 19th century.

Undoubtedly there is trouble ahead. Trump’s lies are the product of a mind apparently unable to recognise the border between fact and fantasy. In his inaugural address he used the word “freedom” just once. Even apologists, who plead for us to see silver linings, acknowledge the cloud. Trump’s distaste for his fellow humans is the other side of the identity politics coin, a landscape of paranoid exclusivity and intolerance, setting group against group. Everyone shouts. No one listens.

Still, the events of the past months have shown that even the unregulated ethical chaos of “post-truth” politics is susceptible to correction. I doubt if we shall hear much more about attendance at the inauguration. The speed and penetration of digital media means that every utterance can be Googled into some sort of reality. Just as the Victorian science revolution played havoc with religious superstition, so the information revolution can now play havoc with political falsehood.

The internet has shown it can magnify the big lie. So it can magnify big truth. It can find a way across the morass of partiality and mendacity to the firm ground of fact. It used to fall to the mainstream media to perform this task. Now the media is everyone and everywhere. Truth may be under attack, but its defenders are armed to show themselves both nimble and strong.