You don’t need to read Douglas Carswell's new book to realise that Ukip was too nasty and thick for someone like him

With the Treasury clamping down on creative tax-dodging wheezes, it is unlikely that the Douglas Carswell biopic will now get funding. In happier times, when people could invest seven and sixpence in a British film and claim £7,250,000 in tax relief after it took seven and sixpence at the box office, it would have been a gimme.

That movie would never have come to a cinema near you unless you lived in Clacton. No one else would pay to see the life story of the affable libertarian who left the Conservatives for Ukip, about whom only two other things of tabloid interest are known.

One is that, as a Tory MP the year before they were leaked, he demanded publication of the MPs’ expenses, which revealed he spent £655 of our money on a love seat in deep moss-brushed cotton. The saucy minx.

The other is that he spent his first 17 years in Uganda, where his father, a distinguished Scottish physician, treated Idi Amin. Wilson Carswell is cited as the inspiration (or one of them) for the doctor in the novel and film, The Last King of Scotland.

You’d have thought a childhood beneath the yoke of a rampant megalomaniac who blamed people of Asian heritage for all his country’s ills would have been ideal training to serve under Nigel Farage. In fact, it did the opposite, instilling in Douglas the anti-authoritarian streak that prevented him kissing the Farage ring.

Almost from the moment Carswell became Ukip’s first elected MP, he and Nigel went at it. Farage’s fighting style is modelled on that of Amin, who, before unilaterally seizing the Scottish throne, reigned for nine years as Uganda’s light heavyweight champ. The skinny, delicate-looking Carswell is more a fencer, preferring rapier thrusts (tweeting a smiling, shades-wearing emoji after Farage’s most recent resignation) to haymakers.

Any speculation about who won their war belongs on page seven of the compendium, “A Thousand Things For Which Life Is Too Short”. Both have now moved on, Farage to touring Trumpland’s outer suburbs in the frantic hope of a call to arms, Carswell to a dual career as independent MP and author. This morning – an entire day after that publicity-garnering defection – he tweeted the cover of his new book. Rebel, the publisher’s spiel informs us, is “a radical manifesto calling for a fundamental change in capitalism and politics”.

In it, Carswell argues that politics has become a cartel “rigged in the interests of a few” (the Love Seat Brigade, we’ll call them for short). This, he believes, has created the anti-oligarchic resentment powering the insurgencies here and in the US, and perhaps soon (may God forbid) in France. “He proposes a profound reform of politics and capitalism to free us from the cartels, listing the practical steps needed to make this revolutionary change happen.”

Best of luck there. Regardless of the system, power has always been the preserve of oligarchic cartels, and democratic politics always cyclically vulnerable to populist risings according to economic conditions. You imagine even Douglas Carswell’s thoughtful, inventive mind will struggle to change that.

But even if Rebel narrowly fails to repeal the immutable laws of power, Carswell has one significant achievement to his name already. He proved that Ukip is too inherently nasty and thick to nurture an intelligent mind opposed to its race-baiting spirit.

For that, Jeremy Corbyn should buy 100 copies of Rebel for all his close political friends (donating the 97 spares to charity shops). Had Farage welcomed Carswell, and tolerated the liberal attitude to immigration he developed from watching Amin expel Ugandan Asians, Ukip might have edged towards the mainstream. It could have become a high-powered magnet for those in the post-industrial wastelands who feel ignored and betrayed by Labour, but are too queasy to vote for an overtly racist party.

Instead, thanks in large part to Farage’s rage at Carswell for wanting to civilise the heathen, Ukip has proved thankfully incapable of reinventing itself as a relevant post-Brexit force. Little has made the election of a second Ukip MP more unlikely than the maltreatment of its first.

Of course, Ukip already has its historic victory. It may not have made much difference to the result, but it enabled the referendum by spooking David Cameron into that cataclysmic misjudgment, and dragged the centre of political gravity far to the right, where this government is now encamped. But it will not destroy Labour, as seemed possible not so long ago, by taking swathes of its Midlands and northern seats.

Douglas Carswell, who may be not as purist or noble as he seems, has read the runes. He jumped before being pushed by Farage and his moneybags Muttley, Arron Banks, or defeated at an election. His three-year stint as the acceptable face of Ukip has been profitable, making him a bankable author, and securing him a microscopic footnote in political history.

All’s well that ends well for Carswell, even if he won’t know for a while if he has also done his bit to realise the dream of his father’s late and least lamented patient. During the 1974 devolution campaign, when Nicola Sturgeon was a wee girl of four, even Glasgow knew no fiercer advocate of Scotland’s independence than its self-proclaimed king in Kampala.