At Karl Marx’s funeral on 17 March 1883 in Highgate Cemetery, north London, a mere nine people were present. The philosopher’s 200th birthday party was rather better attended. On 5 May 2018, in Marx’s hometown of Trier, west Germany, hundreds watched as a Chinese-funded, 14ft statue of the theorist was unveiled. In London, a similar number gathered at the School of Oriental and African Studies for a day-long conference on Marx’s thought. Among those present was the shadow chancellor, John McDonnell.

“Hello, are you looking forward to having a Marxist in No 11?” was how McDonnell recently greeted a business executive. The MP has long spoken of his admiration for revolutionary socialist thinkers. In 2006 he named Marx, Lenin and Trotsky as his most significant intellectual influences (Jeremy Corbyn, by contrast, has confessed to not reading “as much of Marx as I should have done”).

Speaking alongside the general secretary of the Communist Party of India (Marxist), Sitaram Yechury, McDonnell quipped in the opening of his speech: “Can you imagine what my press team said when I told them I wanted to attend?”

The shadow chancellor explained: “There should be no fear in an open and democratic society of discussing the ideas of a political economist and philosopher… whose ideas are actually now exciting interest again” (a recent Ipsos MORI poll found that 49 per cent of the British public believe “socialist ideas are of great value”). To “shy away” from debate, he added, “simply reinforces the regime of self-censorship that the establishment and its representatives in the media have sought to impose”.

It is no accident, as Marxists used to say, that communist ideas have acquired renewed relevance. The 2008 financial crisis, and its baleful aftermath, have undermined capitalism’s claim to superiority. Rather than self-correcting, markets self-destructed. Western economies are marred by what McDonnell called “grotesque levels of inequality” and rising in-work poverty. Capitalism’s tendency to monopoly, or oligopoly, is exhibited by the overweening dominance of Google, Facebook, Amazon and Apple. The “gig economy”, as charted vividly in James Bloodworth’s book Hired, has created a new reserve army of casualised labour. Others are trapped in alienating “bullshit jobs” (to borrow David Graeber’s phrase): labour that serves no meaningful purpose beyond perpetuating the capitalist system.

Some predict that existential challenges, such as automation and climate change, will render Marxist ideas yet more salient. McDonnell cited the Bank of England governor Mark Carney’s warning that mass job losses and wage stagnation could create the conditions for a communist revival.

For Marxism, the demise of the Soviet Union in 1991 has proved to be a blessing, not a curse. The disappearance of an ossified Stalinist bureaucracy – which bore little relation to the stateless idyll Marx envisaged – has liberated followers from guilt by association. Only five ostensibly communist states remain (“market-Leninist” China, Cuba, Laos, North Korea and Vietnam). Marxism has been reclaimed for its original purpose: the critique of capitalism. Yet until recently, it occupied no significant space in British politics. The joke used to be that the UK had more Marxist parties than Marxists: the Communist Party of Britain (which publishes the Morning Star), the Communist Party of Great Britain, Arthur Scargill’s Socialist Labour Party, the Socialist Party (the successor to Militant) and the Socialist Workers Party, to name but a few.

The Labour Party is usually described as owing “more to Methodism than to Marxism”. But it does not follow that it owes nothing to the latter. As McDonnell observed, Marxism was one of the traditions that informed Labour from its “earliest days”. The confusingly-named Social Democratic Federation, Britain’s first Marxist organisation, helped found the party in 1900. Stafford Cripps, who served as chancellor in the Attlee government from 1947-50, was an avowed Marxist in the 1930s and was temporarily expelled from Labour for advocating a popular front with the Communist Party.

There have always been Marxists in Labour but it has never been a Marxist party (or even, by some definitions, a socialist one). Its 2017 general election manifesto was social democratic in nature, vowing to reform rather than replace capitalism. But in his speech, McDonnell couched the party’s pledge to renationalise “water, rail, Royal Mail and energy” in more radical terms: “It’s a significant development as a result of the new exploration of the ideas of Marx.”

McDonnell, who was recently shrewdly described by Momentum head Jon Lansman as both “more ideological and more pragmatic” than Corbyn, has several guises. Depending on circumstance, he can be a prudent “bank manager”, a Nordic-style social democrat or a Marxist insurrectionary.

In the City of London, financiers fear that Labour has a radical “shadow manifesto” lurking behind its 2017 one. McDonnell, who has insisted “there are no tricks up my sleeve”, offered no hint as to future policies. Yet he displayed an abiding faith in Marx’s thought and its transformative potential: “Marxism is about the freedom of spirit, the development of life chances, the enhancement of democracy… We have to cut through this massive weight of historical abuse of his work.” He concluded: “Another world isn’t just possible, another world is in sight – solidarity.”