One of the picture postcards from Labour’s interesting time by the seaside was when Jeremy Corbyn sat in the leader’s seat on the platform taking holiday snaps of his close friend John McDonnell as the shadow chancellor addressed the conference.

This was, in its way, a rather endearing moment. For many years past, the two old comrades spent their conferences addressing sparsely attended fringe meetings that no one in the media, bar possibly the Morning Star, would ever report. Now they were the top-billed acts, the stars of the stage, the recipients of standing ovations. Even the hostile press coverage was rewarding in its way.

They are getting attention like the two of them have never known in their long political lives.

That scene also contained a warning to those many Labour MPs who despair of their prospects under a new management that bewilders them. Of Mr Corbyn and Mr McDonnell, one key figure in the shadow cabinet says: “What I don’t know is what the objective is.” I think I know. Watching them, I think their objective is extremely clear. Jeremy and John have a plan and the plan is to stay exactly where they are.

All party gatherings are two conferences in one. There is the theatrical show on display for the TV cameras and then there is the conference of private conversations in hotel bars and over restaurant tables. Rarely has the contrast between the two been so great. On camera, delegates garlanded their new leader with a standing ovation before he’d started, another when he’d finished and more standers in between. They applauded despite – even because – the speech not mentioning that Labour was rejected by the voters back in May, let alone reflecting on why the party had such a dreadful collision with the electorate. The speech was lacking the craft, polish and structure that both other politicians and we despised members of “the commentariat” look for when judging a leader’s performance. But what was a failure on those criteria seems to have been another commendation of his “authenticity” to many in the crowd. He was speaking to them, much more than he was to the country, and they adored him for it.

Likewise, I found his fans among the delegates utterly unbothered by polling that suggests their hero is the least popular new leader of the opposition since the pollsters started asking the question back in the 1950s. The polls were wrong. Or they were falsehoods manufactured by the capitalist media. Or everyone had underestimated Jeremy at the beginning of the leadership contest and he’d prove them all wrong again.

Off camera, the reaction to the speech from Labour MPs was the diametric opposite of adulation and the response to the polls was a total lack of surprise. Here, for them, was confirmation that their party is blindly marching away from the voters it must attract if it is ever to be a contender for power again. One senior Labour figure characterised the mood among his parliamentary colleagues as “ranging from the clinically depressed to the completely suicidal” – and that was a member of the shadow cabinet speaking.

I ought to make it clear that this is not just the view of the usual New Labourite suspects. It is far from confined to them. I’ve written before about the chasm between leader and parliamentary party. What the conference really brought home is the depth of the terror of the Corbyn experiment among MPs and how widely the horror runs across the parliamentary party from the right through the centre and extending to Labour’s left.

Nor is it the case that the disaffection is concentrated among older MPs who might be accused by Corbynistas of just not “getting it” about the “new politics”. I made a point of listening to many of the new intake of Labour MPs and I found them just as alarmed as their more silvery colleagues. If anything, the fear among younger MPs was more profound because they are the ones who will spend the prime of their political lives in opposition if proved correct in their assumption that Britain is now doomed to at least a decade of further Tory rule. One impressively sparky member of the 2015 intake remarked: “When I was elected I was worried that I would be labelled hard left. Now I seem to be centre-right.” Although sponsored by one of the most leftwing of the trade unions, this MP reported that she was already getting some trouble from activists in her constituency party for displaying insufficient levels of dedication to Corbynism.

The surge in Labour’s membership during and since the leadership contest is having quite an impact at a local level. I collected reports of constituency parties doubling, even tripling, in size. The recruits are made up of a combination of returnees – veteran lefties who deserted Labour in the past – and new folk drawn in by Mr Corbyn. This is his praetorian guard. This is his protection from Labour MPs. This is why he wants to make members much more powerful in party policy-making. This is also why there are very few Labour MPs who think it would be feasible to try to unseat him any time soon. A Westminster coup would make their activists utterly, and understandably, enraged. “They’d string us all up!” says one Labour MP.

The weakness of Mr Corbyn’s position is that he can’t take his fans with him down to Westminster. Away from the warm bath of conference adulation, he will again be surrounded by his hostile parliamentary party. He is currently making a virtue of his minority status within his own shadow cabinet by saying: “I am not a leader who wants to impose leadership lines all the time.” At Brighton, he did not manage to impose leadership lines on his frontbenchers any of the time. As a result, the conference left confusion about what Corbynism now amounts to. He has retreated on several of the big issues on which he fought the leadership contest: Nato, the EU and nationalisation of the energy companies being three of them. Abolition of student tuition fees – another of his signature promises and one very important to his campaign because it helped to draw in a lot of support from the young – has just been made subject to yet another review. But, on the evidence of Brighton, these compromises are not yet hurting him with the people who put him in the leadership in the name of “straight talking” and “honest politics”. Since nothing can be the fault of St Jeremy, his cheerleaders will instead blame wicked Labour MPs for forcing him to retreat.

He did not compromise on the totemic issue of Trident. For saying he could never press the button, he was rebuked by his shadow defence secretary, his shadow foreign secretary, his shadow home secretary and several more members of the shadow cabinet. I can’t remember any other party conference where a leader has been publicly reprimanded by so many of his senior frontbenchers. They basically told us that their leader was stupid for saying that he would never use nuclear weapons because the only reason to possess them is to deter aggressors from firing at you for fear that you will fire back. His position on Trident puts Labour in the novel position of having a leader in rebellion against his own party’s policy. Yet among the people who matter most to him – his supporters among the membership – it was quite clever to demonstrate that there is at least one of his convictions on which he will never surrender.

The straw that some desperate Labour MPs clutch to is the notion that Jeremy Corbyn will come to his own conclusion that he is not up to being leader and voluntarily depart at some point. What I saw in Brighton leaves me very unconvinced by that thesis. “He seemed very frightened by it all at the beginning, but now he’s starting to enjoy it,” observed one senior member of the shadow cabinet. “There’s a glint in his eye.”

Glinting also are the eyes of those who share his brand of left politics and waited out the long wilderness years with him. I called in at a conclave of the Campaign for Labour Party Democracy, the group that was at the heart of the Bennite insurgency in the 1980s. They were in good cheer. “Jeremy is going to give us back our party,” cried an exultant Clive Lewis, the newly elected MP for Norwich South. “We have to go back to our CLPs (constituency Labour parties) and organise.” Kelvin Hopkins, a septuagenarian veteran of the left, proclaimed it “the most wonderful conference of my entire political career”.

The most telling contribution came from Christine Shawcroft, a member of Labour’s national executive committee, who told the meeting: “It’s 30 years since we were defeated. We can’t be defeated again. If we don’t do it this time, it will be 30 more years before there’s a similar resurgence of the left.”

That betrayed some of the nerves at the core of the Corbyn camp. They fear they might blow it. They think this is their once in a lifetime opportunity to take control of the Labour party. It also showed their determination not to miss that chance. Labour’s moderates take note. You won’t get the party back without a fight.