History is written by the victors: this aphorism is usually attributed to Winston Churchill, and is a salutary warning to all those who seek to understand the past. Looking back, we must always make a conscious effort to seek contrary accounts, to rescue the forgotten, the defeated and the eclipsed from what the Marxist historian E P Thompson called “the enormous condescensions of posterity”.

Now, however, we face the opposite peril: of a history framed solely by the “losers” or, more accurately, by their self-appointed tribunes. In this account of the past the “victors” identified by Churchill are axiomatically oppressors, in the wrong and to be deplored.

Witness the unhappy case of Scott Kelly , the retired American astronaut, who last week quoted the Lion of Chartwell in a tweet prompted by Brett Kavanaugh’s successful nomination as a Supreme Court justice . “One of the greatest leaders of modern times, Sir Winston Churchill said, ‘in victory, magnanimity’,” Kelly wrote. “I guess those days are over.”

Citing Churchill en passant to make a general point about civic decency in US politics, Kelly — who is UN Ambassador for Space — can scarcely have guessed what would happen next. Like a meteor storm bombarding a capsule in orbit, furious trolls attacked him on social media for citing a leader who was, allegedly, “just as good as Hitler”, “responsible for the Bengal Famine of 1943”, a “bigot”, and “a mass murderer and a racist”.

Regrettably, Kelly capitulated, responding to this digital bile with abject contrition: “Did not mean to offend by quoting Churchill. My apologies. I will go and educate myself further on his atrocities, racist views which I do not support.” These sad phrases might have come from the pen of a purged party member in the Soviet era, or the mouth of Winston Smith in the final pages of Nineteen Eighty-Four.

A veteran of four space flights, Kelly is a retired US Navy captain whose record of courage and service is awe-inspiring. His nerve held during — for instance — a servicing mission to the Hubble space telescope: a challenge beyond the imagination of most people. Yet, when it came to it, he could not resist the relentless fury of Twitter.

Many of the charges levelled against Churchill are plain wrong. As Andrew Roberts shows in his magnificent new single-volume biography, Churchill: Walking With Destiny, his subject was not responsible, as is so often and so sloppily alleged, for the Bengal Famine which was caused, in fact, by cyclones and regional mismanagement. Indeed, on October 7, 1943, Churchill declared in Cabinet that one of Sir Archibald Wavell’s priorities as Viceroy of India must be to ensure that “famine and food difficulties were dealt with” — a demand he continued to make in his personal contacts with Wavell.

Yet the detail of Churchill’s achievements and alleged flaws is not what really interests his modern detractors. What they seek, absurdly and reprehensibly, is arbitrary, retrospective censorship of one of the towering figures of the 20th century: not perennial reassessment, which is the essence of history, but obliteration. They want it to be culturally impossible for a public figure such as Kelly to quote Churchill without facing a digitally turbocharged wave of Maoist denunciation.

"What they seek is arbitrary censorship, not perennial reassessment, which is the essence of history"

It is essential to identify what is new about this, and what is not. There is nothing new, for instance, in Churchill “revisionism”: in 1993, John Charmley ignited controversy with his highly critical biography, Churchill: The End of Glory. There have been many other such books, before and since.

There is nothing new in “history from below”, either: the scholarly approach to the past, pioneered by Thompson, Eric Hobsbawm, George Rudé and other historians of the Left, that looked at the experience of the masses rather than the deeds of “great men”.

Nor, for that matter, is there anything new in anti-imperialist history, which explores the role of empire from the perspective of the colonised and their heirs. In this context, two of the most thoughtful books of the past year have been Afua Hirsch’s Brit(ish): On Race, Identity and Belonging , and Akala’s Natives: Race and Class in the Ruins of Empire. The challenge that these and other writers present to the sentimental notion of empire still baked into national culture is entirely welcome.

What is new, and dangerous, is the attempt to drown out, usually via social media, anything that does not conform precisely to modern, “woke” ideology and its intolerant parameters. When Nigel Biggar, Oxford’s regius professor of moral and pastoral theology, launched an ethical audit of the British Empire’s record last year, he was subjected to online vilification and personal abuse.

As Trevor Phillips, former chairman of the Equality and Human Rights Commission, said at the weekend, in connection with Biggar’s predicament: “What I worry about is the Stalinist imposition of one reading of history leads to one outcome and that is suppression of free speech.”

This is precisely right. It is a philosophical nonsense to apply 21st-century standards to the past, and to exile from public discourse all those historical figures that do not match the exacting standards of student unions and Twitter mobs.

The whole point of scholarship is to expand the horizons of the mind, rather than to narrow them to the point where every year is Year Zero. The hounding of former astronaut Kelly represents more than the deplorable trolling of an American hero. It is a parable of a growing threat to intellectual life and the freedom of the academy — and a warning of battles to come.