Boris Johnson’s 92,153-vote mandate wouldn’t impress Romania’s Hungarian-speaking minority. The prime minister they most admire, Viktor Orbán, last year won his third electoral landslide with more than 2.8 million votes (49 per cent). He’s due to fly in on Saturday. Hungary’s right-wing leader regularly headlines a nationalist festival that his supporters hold here in Transylvania, and excitement is mounting. His visits have made headlines since 2014, when he used his speech to announce that Hungary should become an ‘illiberal democracy’, and this year’s theme – ‘the future of Europe’ – isn’t likely to rein in the rhetoric.

Orbán has been described by his biographer Paul Lendvai as a ‘master tactician, gifted populist’ and ‘radical and consummate opportunist’ – remind you of someone? Anyone familiar with Boris, however (and I was a close acquaintance for 25 years), will know that the parallels are misleading. Johnson isn’t a nationalist strongman in the Orbán mould. He’s a lot more cavalier than that.

Though a hostility to the European Union has long animated Orbán, he has never suggested that Hungary leave. His demand has been instead that member states be given more leeway. He complains constantly about foreign meddling, but is still conservative enough to implement EU harmonisation measures for the sake of domestic stability (and his cronies profit hugely from EU funds). He also hasn’t seriously challenged EU efforts to regulate ethnic friction in Transylvania.

Johnson’s conversion to Brexit in early 2016, by contrast, has led him to gamble with the British constitution. Far from striving to maintain the Good Friday Agreement, he has alleged that warnings about its fragility are ‘terrible moral blackmail’. That isn’t just self-serving. By effectively accusing the European Union of threatening a return to the Troubles, it turns history on its head. The EU’s existence made peace feasible in the first place. The introduction of the single market in 1993 eliminated the last customs posts, allowing the UK-Republic border to shrink from an obstruction into an irrelevance.

The 1998 Good Friday Agreement rests on leaps of faith as well as years of negotiation. But relative harmony has endured in Ireland, just as Hungary and Romania’s entry into the European Union has consolidated stability in Transylvania. For more than sixty years, the advantages of EU membership have been defusing international animosities from old Franco-German rivalries to the Cod Wars, Gibraltar and the Balkans. They didn’t stop the wars in Yugoslavia and there will always be new flashpoints, but the risks are a reason to back the European Union, not to undermine it.

Johnson privately understands that as well as Orbán. But, unlike the Hungarian prime minister, he is acting as though his great patriotic adventure won’t need the EU at all. Over-influenced and overawed by President Trump, he imagines that the mere threat of no deal could frighten Michel Barnier into concessions. The problem isn’t just that the bluff is so transparent. It’s that it reflects one of Johnson’s signature weaknesses: he can feign optimism and be calculating in pursuit of his personal interests, but lacks the patience for strategic thinking. His notorious pro-having-and-pro-eating-cake Brexit policy wasn’t very funny in the first place (especially because the joke was already eight years old), and the imprudence it epitomises is serious. Johnson is jeopardising a settled constitution and a hard-won peace on the off-chance that something better will turn up.

Orbán has been negotiating forcefully with Brussels for years – he thinks of the process as a ‘peacock dance’ – and his speech on Saturday will doubtless include complaints about EU intransigence that English nationalists would echo. For the little that it’s worth, however, Johnson himself doesn’t take his supposedly radical agenda very seriously at all. He told laughing MPs at a Spectator awards ceremony in late 2016 that Brexit was going to be a ‘titanic success’. Widely reported as a ‘gaffe’, it was no slip of the tongue. Boris easily misspeaks when his mind is elsewhere – as his devastatingly negligent remarks about the Iranian political prisoner Nazanin Zaghari-Ratcliffe illustrated last year – but the after-dinner remark to parliamentary colleagues wasn’t accidentally inarticulate. He has never been sure whether Brexit will end well or badly, but he cares even less.