Jeremy Corbyn’s inability even to travel on a train without incurring public ridicule increases the already strong temptation to award him the lion’s share of the blame for Labour’s predicament. But his antics distract attention from the more fundamental role played by David Cameron and George Osborne in precipitating Labour’s downfall.

For it was Cameron and Osborne who denied to Labour moderates the space they needed to make a success of opposition. Ed Miliband and Ed Balls never had the room required to develop a convincing economic policy.

Under Osborne, the Treasury was still borrowing so much money that Labour could not convincingly promise to borrow even more. Oppositions always find it find this difficult: witness John Major’s successful campaign against Labour’s ‘tax bombshell’ in 1992.

In 1997, Gordon Brown solved the problem by promising to stick to Tory spending plans. Nobody can remember what Miliband and Balls promised in 2015, nor at the time did they manage to enunciate a credible line: the notorious EdStone promised “A strong economic foundation”, without indicating how this was to be achieved.

Labour campaigners often felt a sincere hatred of the Tories, but were unable to explain how they would run the country better. Nor was it easy to persuade voters that Cameron and Osborne were evil reactionaries.

The number of jobs was going up. So, from a low base, was the representation of women and ethnic minorities in the parliamentary Conservative Party. And Cameron had upset many Tories by bringing in same-sex marriage.

So it was difficult for Labour to claim with conviction that it was any longer the more progressive of the two parties. It opposed with vehemence some of the Government’s welfare reforms, but that too was problematic, for it opened Labour to the accusation that it cared more about benefit claimants than about workers.

Cameron, Osborne and other ministers made it extremely difficult for their rivals to occupy the moral high ground. Cameron in particular went through a phase of delivering speeches which were plainly designed to colonise great tracts of the political landscape, with the clear intention of denying them to the Opposition.

This was not a very inspiring spectacle, but was carried through with unrelenting professionalism. Cameron proclaimed himself ‘a liberal Conservative’, and to many people’s surprise, managed to sustain for five years a coalition with the Liberal Democrats, who then proceeded to lose almost all their MPs. That destruction of his partners is another of his generally overlooked achievements.

Miliband and Balls were likewise defeated. They had failed to tell us about the future of socialism. Too much of what they wanted to say was already being said or even done by the Government led by Cameron and Osborne.

In the summer of 2015 Labour held a leadership election in which the three moderate candidates were likewise unable to tell us about the future of socialism. So the party instead opted for the socialist past, embodied in the cranky figure of Jeremy Corbyn, a man who stopped thinking in about 1983.

Gideon Rachman drew attention, in yesterday’s Financial Times, to the similarities between Corbyn and Trump:

“Both are ‘anti-system’ politicians. Both have seized control of their parties by mobilising new groups of activists and voters. The Trump and Corbyn activists despise their parties’ old-guards and often have an undercurrent of violence in their rhetoric. 

Mr Corbyn and Mr Trump are also noted for their sympathy towards Vladimir Putin’s Russia — and their scepticism about Nato. The fringes of the Corbyn and the Trump movements also seem to be infected by anti-semitism, perhaps reflecting the traditional suspicion of the far left and the far right that ‘the system’ is controlled by Jews.”

For Corbyn’s supporters, moderate Labour politicians are hopelessly implicated in ‘the system’, just as for Trump’s supporters, moderate Republicans are.

But at Westminster, the latest manifestation of ‘the system’ in power is Cameron, while in Washington it is Barack Obama. These are the leaders of the civilised, tactful, eloquent, progressive Anglo-American Establishment, which is regarded as such a treacherous sell-out by the neglected, marginalised, old-fashioned outsiders who support Corbyn and Trump, and yearn for a better past.

In the EU referendum, these outsiders helped to deal a fatal blow to Cameron. But Cameron has been replaced by Theresa May: another Conservative, and indeed another Anglican.

The differences between her and her predecessor will be analysed in minute detail, but the similarities are more important. For May shares with Cameron a ruthless determination to show she can do better than Labour what Labour exists to do, namely improve the lot of the poorest members of society.

May intends to win the next election by demonstrating she is a better egalitarian than her opponents. Labour meanwhile is in the grip of activists who despise moderate methods and prefer the emotional thrill of protest politics, in which one has the enormous pleasure of supposing oneself to be morally and intellectually superior, because one has seen through the lies of ‘the system’. Self-righteousness drives out realism.

For the year past the Labour moderates have been routed by Corbyn. But this only happened because they had first been routed by Cameron and Osborne.