It is very easy to predict how the war in Ireland will begin again over a Brexit border in Ireland.

It will start on an overcast day in the early afternoon with a couple of old cars, family saloons, stolen and hidden for months, heading north from County Monaghan crossing the line that supposedly marks the frontier of British Crown rule.

The car at the back will be heavily laden with 500lbs of homemade ammonium nitrate explosives whose basic ingredients, farm fertilizer and diesel fuel, will cost no more than $800 dollars.

Nor are the men in the cars, a scout vehicle and the car bomb, particularly special. They will be foot soldiers, mechanics, easily replaceable by others. They will call themselves republicans, dissidents, but their political beliefs—that the British State has no legitimate right to rule in Ireland against the will of the Irish people—would be widely shared across the island.

Read more: Top IRA informer arrested in investigation of 30 deaths

British army in riot gear in Northern Ireland during the Troubles. Image: WikiCommons.

British army in riot gear in Northern Ireland during the Troubles. Image: WikiCommons.

Of course, unlike the men in the car, the vast, vast majority of the Irish don't care enough to do anything about those beliefs and generally ignore Northern Ireland altogether. That was until Brexit came along with all the threats to Irish trade and talk of the re-imposition of border checkpoints.

Since the 2016 referendum on leaving the European Union, British politics, and the warring factions within British Prime Minister Theresa May's Conservative Government has been convulsed in arguments over what kind of future trading relationship the UK will have with its former European partners.

A 'hard' Brexit will automatically entail some form of border controls along the land border between the Irish Republic and Northern Ireland to prevent goods illegally crossing between what would be two different economic trading zones.

But for hardline Brexiteers in London, a 'soft' Brexit without border controls would defeat the whole purpose of breaking away from the existing trading relationship with the European Union.

Prime Minister of Britain, Theresa May.

Prime Minister of Britain, Theresa May.

The Irish border has become a pawn in a wider English nationalist political game.

The men in the cars won't be listening to the ins and out of Tory Westminster debates nor will they stop at the nominal line than marks Her Majesty's rule. They will drive on past whatever is being termed "a frictionless border" deeper into Northern Ireland until, ten or twenty miles in, they reach a town like Cookstown, Magherafelt, or Portadown. Their target.

Read more: Senator Mitchell warns of major problems if Northern Ireland governing issue not sorted out

Small obscure market towns no-one in England has ever really heard of, tidy places, proud of their Protestant history and therefore less likely to evoke sympathy if there are any civilian casualties.

And we know that the bombers will choose these places because they have chosen them before in the last set of Troubles.

The men will park their car bomb as close as they can to any symbol of Crown rule in Ireland; a courthouse, a police station, a government office deemed to be processing electronic border import/export files. The accusation alone will be enough because none of the perpetrators, or their sympathizers, will believe the subsequent denials.

The bomb team will be careful to give an adequate warning to absolve themselves of the blame for any of the 1998 Omagh bomb style casualties that killed 29 civilians and damned the Real IRA into infamy. The bombers' aim will not be to kill civilians but to show the world that the Irish rebellion against the illegitimate rule of the English Crown in Ireland has begun again.

If the bombers succeed their bomb will go off sending a deadly whirlwind of destruction through the town's market square, ripping off roofs, shattering windows, destroying buildings and businesses. The sky will rain glass and the streets will be paved with its broken glitter. The damage will run to tens of millions of dollars.

There will be outrage, universal condemnation from the Irish Taoiseach, the British Government, even Gerry Adams and the Sinn Féin leadership. Vows that no stone will be left unturned in the hunt for the bombers.

Leading British Tory politicians will fume out loud about the perfidious Irish in the same way that similar foolish British politicians have fumed about the Irish for the last two centuries. Everyone will condemn the bombers in public, at least.

But in private many in Ireland will savor the schadenfreude, make a holiday in their hearts, because of all the ignored 'we told you so.'  All the vacuous sophistry of the Westminster Brexiteers now blindly repeating the same Anglo-Irish errors of the past.

Read more: Defending the tricolor in light of Strabane and Derry's proposed St. Patrick’s Day parade

British soldiers welcomed my loyalists in Northern Ireland. Image: WikiCommons.

British soldiers welcomed my loyalists in Northern Ireland. Image: WikiCommons.

The Irish people will not support the bombers but they will not support the British Government either.  Violence and equivocation over its use an alternative political weapon were as intrinsic to the Troubles as soft Irish rain. The bombers, a tiny gathering, will, despite the subsequent arrests, be numerous enough to endure.

To defend an indefensible border, Northern Ireland's PSNI police force will again become a frontline paramilitary force, armed defenders of the realm against Irish rebels, in borderlands even the British Army deemed too dangerous to patrol. There will be landmine attacks, more bombings,  outrages, troubles. The war will escalate.

It is not just a matter of geography. Aside from the Democratic Unionist Party, there are no votes in Ireland for a British border. Trying to police such a border in any way, taxing goods, inspecting lorries, sending electronic waivers, is an assertion of foreign British rule against the will of the vast majority of the Irish people.  A perfect opening for those who would prefer to bomb rather than argue about border controls.

How will Brexit effect peace in Northern Ireland? Image: iStock.

How will Brexit effect peace in Northern Ireland? Image: iStock.

The legacy of 800 years of British rule in Ireland—genocide,  famine, wars, outrages and troubles—is written in word, stone and memory but not indeed since the 1998 Good Friday Agreement. Those long dark centuries teach us all that British rule in Ireland cannot be maintained in peace without the acquiescence of the Irish Government and the Irish people.

It is a lesson that the current British Conservative Government seems determined to ignore and it will just as surely as the sun rises daily in the East re-engender war in Ireland.

Kevin Toolis is the author of "My Father's Wake: How the Irish Teach Us to Live, Love and Die" published by DaCapoPress, Feb 27, 2018. He reported on the Troubles for two decades and wrote an acclaimed chronicle "Rebel Hearts: Journeys Within the IRA's Soul."

Read more: Families of 1974 Birmingham bombing victims seek names

The aftermath of the 1998 bombing of Omagh.