When I lived in the Soviet Union in my early twenties, I developed a personal hostility to socialism. I saw the misery it had visited on that society – the political, spiritual and economic harm. I understood at first-hand how the secret police corrupted personal and public life, how state propaganda denied freedom of thought and how the regime hid the slaughter and imprisonment of millions of its own people.

I came to the conclusion that whichever totalitarian power had survived World War II – Nazi Germany or the Soviet Union – they would probably have looked much the same by the time of their demise. I never understood why Westerners did not – or could not – see the closeness of Left and Right extremes and the similarities between their fellow travellers. So when I hear people like Labour’s Shadow Chancellor John McDonnell praising Marx – he has said: “I’m honest with people. I’m a Marxist” – it concerns me.

In the UK we see politics as being linear; if you are hard Left, you are the opposite of hard Right. In fact, both share many traits: acceptance of their political violence, denial of individual liberty and indulging in conspiracy theories. Perhaps most critically, many of them at their heart share a resentment and even hatred of capitalism and Jews – or both.

Perhaps McDonnell doesn’t realise it, but Karl Marx’s conspiratorial view of the world is at the rotten root of both hard Left and Right. Marx helped provide the intellectual base for both the Holocaust of the Jews and the Holodimir – mass starvation – of the Ukrainians. Between them these acts claimed the lives of more than ten million people.