For some years now, mainstream British politics has revolved increasingly obsessively around the question of how to stop Nigel Farage. What started a decade ago with Brexit may yet end in a general election that boils down to one question: do you or don’t you want to risk putting this man in Downing Street? That said, we still know surprisingly little about what a Reform government might mean in practice.

Of course, it might never happen. But if it did, what exactly would Farage do with a majority that enabled him to fulfil his wildest dreams? And how well would an unwritten British constitution, still heavily reliant on good chaps voluntarily being good chaps, cope with full-fat populism?

This is terrifically rich territory for a book, but what makes Times reporter Peter Chappell’s take so readable is its boldness. Though based on conversations with civil servants, Reform insiders and others, it’s pitched not as a piece of conventional analysis but as a story: a lively and often witty political thriller that both is and isn’t fiction, sketching the imagined arc of a Reform government from triumph to disaster.

It’s a high risk approach that requires an author to back his hunches, not least about how the world might look at the next general election (by which time Chappell assumes Keir Starmer will have been  replaced, and Donald Trump succeeded on health grounds by JD Vance). Though some of his bolder bets – that the head of MI5 would just delete embarrassing bits of Farage’s file so as not to upset the new PM, or that Peter Kyle would end up acting Labour leader after a defeat – seem rather far-fetched to me, others are carefully grounded in events from the recent past. Meanwhile there’s enough gossipy detail about the coffee stains on Downing Street carpets, the weird way a particular character dresses, or personality clashes within Reform to lend it the smack of authenticity.

Given the party’s plans for vast areas of British national life remain at best hazy, the drama focuses on three issues where its ambitions are clear: immigration, scrapping net zero and cutting taxes. What follows is a tale of irresistible force hitting immovable objects that makes the Liz Truss era look positively well organised, with an unexpected role for (no spoilers) an old enemy returning in a new guise.

His semi-fictional Farage’s first act is to withdraw from the European convention on human rights and disapply the 1951 refugee convention, clearing the path for mass deportations, abolishing indefinite leave to remain and sending navy gunboats into the channel to turn back small boats. From there he moves on to war with the BBC. Events unfold at a zippy pace, with drier factual material about, say, what powers parliament has to contain him woven into the narrative.

Though the focus is firmly on power struggles in Whitehall rather than on the human consequences for vulnerable people, this is at heart a moral fable in the sense that it’s constructed to convey a warning: chiefly, that the British system concentrates startling amounts of power in the hands of a prime minister with a majority and no squeamishness about using it. A future Prime Minister Farage could legally go to war without consulting parliament, fire civil servants who block him, and potentially wield sweeping emergency powers if he chose to invoke the civil contingencies act (for example, in response to mass protests). The biggest constraint on his ambitions might come not from parliament or from the streets, but simply from logistics, or the tendency for ideological wishlists written on the back of fag packets to collapse on contact with reality.

Without giving too much away, the fault lines it identifies within Reform – including the risk of infiltration by extremists, represented here by a strictly imaginary character who nonetheless strongly reminds me of a real person hovering somewhere near its fringes – are realistic enough. As a “nonfiction thriller”, it’s convincing. As an analysis of Reform in power, my only worry is that Chappell may be too optimistic about the speed with which things fall apart. Let’s hope he’s a better forecaster than me.