To most – dare I say all? – of us who worked as journalists in Northern Ireland during any part of the last quarter of the 20th century, the idea that a mainstream British political party could even contemplate teaming up with the DUP (Democratic Unionist Party) beggars belief. In part, that shows how the times have changed; in part, it shows the dangers of airbrushing the past.

It seems extraordinary to need reminding that the DUP was the party of fundamentalist, sectarian, street-fighting Protestantism, and the vaunting Rev Ian Paisley its figurehead. Mind you, he was always a good media sport.

Maybe in the future the Democratic Islamist Party (DIP) will be propping up another government of British politicians who conveniently choose to forget their nation’s history

While I was in charge of BBC Northern Ireland’s weekly current affairs programme Spotlight (the launch pad for, among others, Jeremy Paxman and Gavin Esler, my then colleagues in Belfast) Paisley and his church were running a “Save Ulster from Sodomy” campaign.

I wanted to entice him into a studio debate with the main – and very brave – face of the local gay community at the time. I imagined that the Rev Ian would bring down his curses on the mere suggestion of sharing a studio with such perversion.

But no, he instantly accepted and, as I recall, it was rather a good, if unenlightening, entertainment. I know I shouldn’t have wanted to laugh when the “big man” cried out – in his unique voice and no-holds-barred accenting – “Save Ulster from Sodomy” but it was almost comedic. Though not so funny if you happened to be a gay person wanting to live out your life in peace but terrified out of it by a gang of bigots.

Ian Paisley leads an anti-Catholic demonstration from Trafalgar Square to Downing Street, London in 1967. Photograph: John Downing/Express/Hulton Archive/Getty Images

Bursting onto the Northern Irish political scene in the late 1960s as the Protestant resistance to the civil rights campaign for equality for the North’s minority Catholic population, Paisley, let’s not forget, was an extremist, with links to some particularly unpleasant people. (Ed Moloney’s Paisley; from Demagogue to Democrat? is the definitive account.)

That extremism, both political and religious, continued through the Troubles; it not only divided loyalists from republicans but also loyalist from loyalist, Protestant from Protestant. It was the prime wrecker of all initiatives proposing political compromise – though not the prime wrecker of lives and property, which dishonour remains with the IRA followed by other paramilitaries.

Paisley’s extremism was the prime wrecker of all initiatives proposing political compromise – though not the prime wrecker of lives and property, which dishonour remains with the IRA

Yet here we are; the DUP’s leader, Arlene Foster – not, it should be said, a religious Paisleyite – and her colleagues hold the future of our nation in their hands. In two years’ time, their pact with Theresa May – on the rash assumption she’s still there – has to be renegotiated in the aftermath of the Brexit negotiation deadline.

Whatever one’s view of Brexit, the succession of madnesses that remorselessly propel the UK of GB and NI into lunatic acts of self-destruction shows no sign of abating for as long as political outcomes can be decided by the successors to the Rev Ian.

Ireland is a particularly enlightening example of how the past can not only be conveniently forgotten but can continue to impinge. In 1981 I made a World in Action documentary on the first IRA hunger strike in the Maze prison. It contained a scoop – we were the first film crew ever allowed into the hunger strikers’ cells as they lay staring at cell walls smeared with their own excrement as a result of the much longer-running “dirty protest”.

Compromise seemed impossible. Thatcher was resolute, allowing 10 hunger strikes to die before a paper compromise was finally agreed. For months, dustbin lids were rattled, stones thrown and rifles fired on the streets of west Belfast. Three years later, Thatcher just escaped death in the blowing up of the Grand Hotel in Brighton.

There seemed no imaginable meeting point between irreconcilable opposites. It was inconceivable then that, 10 years on, the first tremors of a peace process that actually ended up succeeding would begin to be felt. That would require a remarkable forgetting of the past.

Martin McGuinness and Gerry Adams became men of peace – even the most indefatigable of journalists with an accumulation of evidence failed to incite any governmental desire to trawl over the nastier details of their paramilitary careers. The same went for the other side. The early career of Paisley the wrecker was airbrushed out of history. It helped that he and McGuinness were both men who could display great personal charm when they chose to.

My novel Woman of State is inspired by the different outcomes of that process – my woman becomes involved in something terrible, gets away with it and then finds herself a target. Two decades later, when she becomes a rising politician, these ghosts return to haunt her, bringing new casualties in their wake.

We have no ambivalence when the sins and betrayals of purely criminal pasts rebound, sometimes decades later, on lives in the present. We tread less certainly when those sins are not purely “criminal” but associated with conflict where the distinction between “good” and “bad” turns grey.

That ultimately is how the former paramilitary leaders in Ireland have got away, literally, with responsibility for murder. Maybe in a future generation the Democratic Islamist Party (DIP) will be found propping up another government of British politicians who conveniently choose to forget their nation’s history.

Simon Berthon is a TV producer, director and author of three history books. He was editor of BBC Northern Ireland’s Spotlight series and Head of Current Affairs NI. He has just published a political thriller, Woman of State (HQ, £12.99), about an Irish woman who shakes off her IRA family past to become a Minister at Westminster… But whose side is she really on?