In the course of writing my first book, Not Buying It — The Facts Behind Fake News, the overlap between what I was writing about — predominantly fake news and disinformation in the modern world — and much antisemitism struck me. Indeed the oldest hatred, turned out to be one of the oldest forms of fake news as well, dating back to Martin Luther in 1545, if not earlier.

Whether it is the classic antisemitic tropes of the all-powerful, plotting, money-grabbing Jew or the modern phenomenon of antisemitic anti-Zionism and conspiracies about Mossad, fake news and post-truth thinking sits at the heart of it all.

Social media has, of course, had a huge effect on all of this. No longer are crank antisemites confined to strange meetings and newsletters.

Their bile and hatred can be spread all too easily now. Far-right fascists congregate on websites like 4Chan while hate spreads on mainstream sites such as Twitter and Facebook. There, prominent Jewish figures like Luciana Berger MP and others are subjected to torrents of abuse because of their religion.

Fighting back is hard and will take some time — but fight back we must. Whether it is through teaching children media literacy in schools, putting pressure on the social media companies to take action against hatred or by simply presenting the facts, now is not the time to sit back.

The eminent historian Deborah Lipstadt has long been on the front line of this fight. She recalled the incredulity with which her refusal to appear on television with a Holocaust denier was met by the producer trying to book her. “She found it hard to believe that I was turning down the opportunity to appear on her nationally televised show,” wrote Prof Lipstadt at the start of her book Denying the Holocaust.

Professor Lipstadt explained that far from this being a one-off, she has had many such requests. She wrote that her refusal “is inevitably met by producers with some variation of the following challenge: Shouldn’t we hear their ideas, opinion or point of view?” Her contention, rightly, is that there is no point of view on the Holocaust — simply fact and (antisemitic) fiction.

It should not require repeating but we know that six million Jews were murdered during the Holocaust, alongside millions of homosexuals, Roma and communists. We know that gas chambers at Nazi concentration camps were one of the key ways this horror was enacted. These are not points of view to be contested. Claiming otherwise is not only antisemitic and vile but simply untrue.

However, in 2000 Prof Lipstadt and her publisher, Penguin Books, were sued for libel by the Shoah-denying historian David Irving after she branded him an antisemite. Irving lost in a landmark court case.

Famously, the truth prevailed on this occasion and Prof Lipstadt won.

The academic David Hirsh, a senior lecturer in sociology at Goldsmiths University in London, who has written extensively about left-wing antisemitism, said in an interview that “Irving was busy trying to portray himself as the victim of the Jews and the victim of the publishers and the victim of Lipstadt and [Anthony] Julius, the big Jewish lawyer.” He was invoking antisemitic memes even as he tried to use the courts to free himself from the label of Holocaust denier. He represented himself in court and tried to distort the situation and portray himself as the victim, even though he had brought the case.

Prof Lipstadt may have won on this occasion but victory for the truth is far from guaranteed.

Antisemitic propaganda is not new. Hatred of Jews based on conspiracy and falsehood goes back centuries, to when the Romans sought to establish Christianity as the sole religion, replacing Judaism. In the 14th century, as the bubonic plague ran riot, the public blamed the Jews for its spread based on the falsehoods that many already believed.

Later, in 1545, Martin Luther, the founder of Protestantism, published a treatise called On the Jews and Their Lies, which included the claim that Jews thirsted for Christian blood and should be killed. Martin Luther told Christians to “guard against the Jews, knowing that wherever they have their synagogues, nothing is found but a den of devils in which sheer self glory, conceit, lies, blasphemy and defaming of God and men are practised most maliciously”. He went on to say that Jews “are nothing but thieves and robbers who daily eat no morsel and wear no thread of clothing which they have not stolen and pilfered from us by means of their accursed usury”. Such lies and tropes exist to this day.

The Nazis deployed ever more poisonous propaganda during the 1930s, including reprinting the Martin Luther document,to create a backlash against Jews. Professor David Welch explained for the BBC that “the Jewish stereotypes shown in such propaganda served to reinforce anxieties about modern developments in political and economic life, without bothering to question the reality of the Jewish role in German society”.

Maintaining that there will be £350 million more a week to spend on the NHS if Britain leaves the EU or that Hillary Clinton is seriously ill clearly pales into insignificance when compared to propaganda that led to the genocide of six million members of a particular religion. However, at its root, there is the same contempt for the truth, the same malice aimed at the “other”.

It should be no surprise, then, that time and time again, classic antisemitic imagery reappears in modern fake news.

David Hirsh explains that “people on the left have been doing it for ten, 15, 20 years. People on the little dusty corners of the left have been doing it for longer. And it was we on the left who took it into the mainstream.”

With the ascent of Jeremy Corbyn to the leadership of the Labour Party, left-wing antisemitism became a full-blown crisis. There are a variety of incidents and issues concerned with this that require unpacking. Some relate to what is known as antisemitic anti- Zionism, in which the perpetrator seeks to hide antisemitism behind criticism of Israel.

Others are just fully fledged conspiratorial antisemitism, in a more traditional vein.

First, Corbyn ally Ken Livingstone was involved in a huge row over antisemitism in the summer of 2016 for repeatedly asserting that Adolf Hitler “was supporting Zionism before he went mad and ended up killing six million Jews”. Indeed, Mr Hirsh has coined what he calls the Livingstone Formulation in honour of the former mayor of London. In his book Contemporary Left Antisemitism, he explains that “the Livingstone Formulation conflates everything — criticism of Israel but also other things which do not seem to be so legitimate”.

He cites as a prime example how Mr Livingstone compared a Jewish newspaper reporter to a concentration camp guard before pivoting to attack the government of Israel when he was criticised for doing so.

Like Irving, Mr Livingstone tries to portray himself as the victim in these incidents. In his autobiography, he recalls that episode. Unrepentant, he remembers weeks of clashes as a whipped-up media row in which countless people, including his future mayoral rival Boris Johnson, supported him and urged him not to apologise. He even claimed that “the phrases ‘behaving like a concentration camp guard’ and ‘jumped-up little Hitler’ are common jibes in Britain” and that “no journalist had ever complained before”.

Things took a turn for the worse in 2018. In March of that year, it emerged that Mr Corbyn had been reported to be a member of and active in a number of Facebook groups in which antisemitism and Holocaust denial were rife. He was also found to have supported a mural that contained clear antisemitic imagery. Then came a very weak statement of apology from Mr Corbyn, in which he insisted on his “total commitment to excising pockets of antisemitism that exist in and around our party” and said he’d never noticed the antisemitism in the mural, having only glanced at it quickly.

Not surprisingly, this fell far short of what communal leaders felt was required, and they continued with their planned protest in Parliament Square, which attracted 1,500 people.

At every juncture, supporters of Mr Corbyn insisted there was no problem and, crucially, that it was all a conspiracy cooked up by powerful Jews to try to dethrone their glorious leader.

This is an edited extract from ‘Not Buying It’ by Charlotte Henry, available now, published by Unbound