The new prime minister insists blind ambition is enough. Like Peter Pan, if we do believe, we do, we do, then it will come true. We can have a new exit deal with the European Union within 99 days without the “undemocratic” Irish backstop because he wills it so. This Tinkerbell delusion is about to be tested on the wheel of harsh reality when Boris Johnson goes to meet his European colleagues. But even his first step has backfired. When he, unwisely, upped the ante by making refusal of the Irish border backstop a precondition for talks, the EU negotiator Michel Barnier immediately rejected the move. Now Johnson will have to back down even to get a meeting.

The prime minister’s strategy, however, remains clear: he will combine public threats and private charm. First, he will frighten Europe by giving every impression of going hell for leather for a no-deal Brexit. He has certainly appointed the right team to frighten them – Dominic Raab, Michael Gove and Dominic Cummings. Like us, EU leaders have seen the movie. And then he hopes the leaders will melt in the face of his personal charm when he comes to visit them.

Bluster and bullshit is fine in the public domain but in the Kanzleramt, it will count for nothing

I spent 10 years negotiating with EU leaders alongside Tony Blair, and there are a number of reasons I believe Johnson’s strategy will not work.

First, the civil service. There is no continuity in the leading ranks dealing with Brexit. Britain’s chief negotiator, Olly Robbins, has been hounded out and the cabinet secretary has only managed to hang on by the skin of his teeth. Johnson has appointed a raft of Brexiteer special advisers but they cannot coordinate Whitehall, or go to Brussels to negotiate.

Even more importantly, in the face of this anti-civil service crusade, who will prepare honest briefs for the prime minister? It is the duty of civil servants to tell truth to power, but who can blame those who remain if they pull their punches in the face of threats to their career? Johnson will go into the talks without a realistic map of the minefields, or an experienced adviser at his side.

Second, when he gets into the room with his opposite numbers, the charm that has worked so well in the past on young women and his angry bosses is likely to wilt. He inspires no trust in his European counterparts and he has no allies.

Brussels is making it clear he should go to capital cities first so he can be disarmed of his irrational exuberance. When he goes into Angela Merkel’s office in the gleaming Kanzleramt in Berlin, she will listen politely to what he has to say, looking for anything new or any sign of room for him to wriggle out of the unwise promises he made to party members to get elected. She will want to find a way of avoiding a no-deal Brexit and will suggest ways of softening the backstop, but she will not get rid of it. Leo Varadkar in Dublin will be equally polite, but no amount of charm will persuade him to drop the backstop. He has already made it clear that, in his view, Johnson’s “confidence and enthusiasm is not a substitute for a European policy”.

Third is the problem of logic, which does not bend to charm. The backstop has been agreed because if we leave the EU there will otherwise have to be a hard border in Ireland. It doesn’t matter who builds it; either the UK does or the Irish will have to. Technology can make it possible for lorries to cross the border more quickly, but that isn’t the problem. The problem is identity, which is at the root of the Good Friday agreement, and that is not solved by a faster border.

The ruse of a “standstill” deal, where Britain continues to enjoy all the benefits of the single market while being outside it – which Johnson has promoted on the campaign trail – will be immediately dismissed. In addition, Merkel will point out that the Canada-style free trade agreement he wants will necessitate a return to the original backstop, where Northern Ireland remains inside both the single market and the customs union, with a border in the Irish Sea. Furthermore, it will have to be permanent. A hard Brexit otherwise requires a hard border. That will be anathema to the DUP, on whose support he depends.

Johnson has been theatrically critical of Theresa May’s approach to Brexit, but he seems to be repeating exactly the same mistakes. He has made a series of contradictory promises to different people and his bluff is about to be called. As soon as he gets into the room with serious politicians they will confront him with the logic of his position and he will have no answers. Johnson’s mixture of bluster and bullshit is fine in the public domain, but in the quiet of the airy office on the third floor of the German chancellery it will count for nothing.

When Johnson returns empty-handed from his European tour he will – given his lack of a working parliamentary majority for a no-deal Brexit – face two choices. He can go either for a general election or a referendum. Although the latter would be the right choice for the country, it looks likely he will go for the former. The polls will show him that with the progressive vote split, with Labour down to 20% and the Lib Dems at 20%,, he could win a landslide in the first past the post system with an electoral understanding – even an informal one – with Nigel Farage. And he will know that if he waits too long into next year for an election, the recession will have begun to bite.

For those of us who find it hard to stomach the idea of five years of a Johnson-Faragist government and the hardest of Brexits, the only possible way of stopping it is a coalition of progressive forces, from disenchanted moderate Tories to disgusted moderate Labour plus the Lib Dems and others, running on a common platform with the aim of forming a government of national unity.

• Jonathan Powell was Tony Blair’s chief of staff from 1995 to 2007