I heard the first chants of 'Ooooh Jeremy Corbyn' within hours of arriving in Glastonbury. You'd hear it everywhere, from late-night raves to rock sets in the afternoon. It was ubiquitous.

Sometimes it was alarming, like when it broke out at a Smiths tribute band gig. The group changed the Lyrics of 'Panic' from "hang the DJ" to "hang Theresa". Because it's the Smiths, the audience was overwhelmingly male. The sight of thousands of men in a tent chanting for the execution of a female politician they disagree with was genuinely disturbing.

Sometimes it provoked interesting moments of political contact. A crowd were chanting it outside the toilets at one stage and an older man angrily informed that they didn't know what they were talking about. "He lost the election," he informed them, exasperated.

Sometimes it was impossible to feel resentful about it. I spoke to more than one person over the course of the festival who had never voted before Corbyn. They were genuinely inspired by him. The crowd at Glastonbury generally shares the same values as me. After the nativist bludgeoning of the last 12 months, with all the mean-spirited nonsense about the somewheres versus the anywheres, people who believed in a kind, open society felt hope. Who could possibly resent them that?

But regardless of the context it is strange, unhealthy and dangerous to chant the name of a politician with anything other than mockery. It is the cult of the leader over the assessment of policies. Nothing good can come from it.

Britain was never a utopia of policy-only debate. Presentation has always mattered in politics, from as far back as the records go. And yes, Britain was already becoming increasingly presidential before Brexit. People put that down to Tony Blair but Margaret Thatcher benefitted from it too. And it's not like Winston Churchill refused to trade on his reputation either.

But something new is happening across the political divide. Theresa May ran for election not on a manifesto, or a Brexit plan or even as a party leader. She ran personally. Insofar as it was possible, she removed all mention of her party from her campaign. The message was: put your trust in Theresa. Every vote for her 'strengthened her hand'. This was not about a personality selling the policies. It was about a personality full-stop. You'd find out what the policies were after the election.

In the future, historians will marvel at how the Conservatives tried to build a cult of personality around someone who simply did not have one. You might as well try to build a car around a tree. But that is not the lesson the Tories should learn from all this. They should instead look at May's current problems and notice how connected they are to the personality strategy.

Constitutionally and democratically, there is nothing wrong with what May is doing with the DUP. The votes for her party plus those of the party she is doing a deal with allow a majority in the Commons, so it's fair she tries to govern. That is not some arbitrary rule. They have that majority because lots of people voted for those parties. This is decent, moral electoral arithmetics.

The reason it has such a rank smell of filth is precisely because she personalised the proposition. She didn't ask for a mandate for the party. She asked for a personal mandate on her judgement. She did not get it. And yet she is still there. The rules she laid down demand she goes, even if those of how we do politics do not.

Now we are seeing the same thing with Corbyn. A cult of personality is being built around him. Again, it is not clear that his personality can sustain it. On the plus side, he is good on TV sofas. He appears to have an actual human personality, which is increasingly rare in Westminster, and he is intellectually present in the conversation, which is also rare in a generation of politicians who have been taught to deal entirely in empty slogans.

His oratory, however, is really quite poor. Given the constant chanting of his name at the festival, I expected his speech at Glastonbury to be like the second coming of Christ. I thought he would stand there like Hugo Chavez while the crowds sang his name for minutes at a time. In reality, there was some chants at the start and end and some decent applause. It was far below the level of adulation you'd expect if you had been there for the days leading up to it. And that was for good reason. His speech was like a series of Hallmarks cards stitched together. It could be summarised as: 'Wouldn't it be good if we were all a little nicer to one another?' To be fair to him, I am genuinely unsure that the Tory leader holds the same position, but a political programme this is not. People are entitled to plans and details, not just platitudes which everyone would agree with. The need for Corbyn was more important than his qualities. Up on that stage he seemed like a cork in the sea, bopping up and down due to historic forces outside of his control.

His approach to politics is not so distinct from a standard politician. He evades questions, he pretends things are not in his power when they are, he dodges responsibility, he fails to live up to the promises he has made. He makes the same compromises other politicians do, as my colleague Chaminda pointed out on this site yesterday.

But you can't hold politicians to account unless you put hero worship to one side and assess them as vigorously as their opponents. If you really believe in the values Corbyn expresses then chant them and make sure he sticks to them.

Whatever you do, do not chant his name. There is no leader to save you. There never will be. Every new saviour, from Blair to Corbyn, will disappoint. They will try to keep things from the public. They will act in their party's interest over that of the country, or their own over that of their party. They will invent enemies to consolidate their position. They will see an ultimate destination and promote information which makes the public more likely to support it. They will make a trivial but embarrassing mistake and then try to cover it up, which usually entails a more serious and reprehensible mistake. They will prioritise what is easy over what is right. And eventually, when they have been in power for a while, they will lose touch, they will forget what it was like not to have power. And then they will start to behave very badly indeed. This seems to happen to everyone. There is no cure to the human condition.

That's why most advanced democracies outside the US – which puts far too much focus on the president – dampen passion around the individual and instead put it on policies. It's why dictatorships so often put a frenzied focus on the individual, from the national insanity of North Korea to the emotional pull of Latin American generals.

Hero worship and the cult of personality are as dangerous on the left as the right. This new period of British politics should be brought to a rapid end. It is fundamentally authoritarian – whichever side of the political debate it is on and whoever it is directed towards.

Ian Dunt is the editor of Politics.co.uk. His book – Brexit: What The Hell Happens Now? – is available now.

The opinions in politics.co.uk's Comment and Analysis section are those of the author and are no reflection of the views of the website or its owners.