Dublin - Mervyn Johnston, 79, would rather forget the conflict in Northern Ireland.

"I've been blown up a few times," says the Northern Irishman as he sits in the office of his car repair garage and looks at the bridge that crosses the Termon River.

The waterway separates the Republic of Ireland part of the village of Pettigo from the Northern Ireland part.

The armed conflict

In the past, there had been border guard posts on both sides. And they might be back soon should Britain not strike a deal on its departure from the European Union before March 29.

Johnston points to his garage. "The main garage ... was blown up completely twice," though nobody was injured in the blasts, he says. "I'm lucky that I'm still here," he comments.

Johnston is referring to the Troubles, the bloody civil conflict in Northern Ireland from the 1970s through the 1990s. Then, Catholic fighters waged war against British soldiers and Protestant loyalists in a bid to get the region known as Ulster united with the Republic of Ireland. Some 3,700 lives were lost in the years-long conflict.

Johnston says he was happy when the Good Friday Agreement of 1998 put an end to the armed conflict.

But now, the shadow of the past is creeping into peoples' minds with the prospect of Brexit. "There will be a few individuals who just want an excuse to get this trouble started up again," Johnston says, citing a car bomb explosion just a few weeks ago in the border city of Londonderry.

Johnston does not believe that things will be as bad as in the past.

But if there is no Brexit agreement, he says that he is sure there will then once again have to be border controls.

Border controls

James Gallagher has already had a taste of what could come. The 60-year-old runs a small supermarket in the Republic of Ireland part of Pettigo. He recently received mail from the government in Dublin informing him that he may have to fill out import documents if he has goods from Northern Ireland in his store.

Gallagher shakes his head at the prospect: For such a small outfit like his, this would make little sense.

Instead, he will cancel the deals with his Northern Ireland suppliers and sell fruit and vegetables obtained in Ireland.

Both London and Dublin have repeatedly stressed that they want to avoid a hard border at all costs. But it remains uncertain what is going to happen if there is no agreement on the Irish border issue.

"I think that it's one of these things that you don't want to say it, in case by saying it you make it happen," says Brian Lucey, an economics professor at Trinity College in Dublin.

Economic dependency on Britain

"The reality is, everybody knows in the event of a complete chaotic no-deal Brexit, there is no situation in the world where two customs unions - one being the EU customs union and the other being the internal UK customs union - where they push up against each other, where there isn't some kind of border checks."

In economic terms, a no-deal Brexit would be tough on Ireland, but not a catastrophe, Lucey feels.

For decades now, Dublin has been working to reduce the country's economic dependency on Britain. This process would be sped up, Lucey says. Over a 15-year period, Ireland would lose some 7 per cent of its economic growth, or one-third the extent of the damage that the country suffered from the financial and economic crisis of 2008-2009.

But of much greater weight would be the effect on employment.

"You're looking at maybe 40,000 to 50,000 job losses, which is hugely problematic for those who lose their jobs in an economy where there's 2 to 3 million people employed," he said.

Still, it would not be the catastrophe that makes Brexit backers in Britain believe that Dublin, in the end, will give in.

In any case, reinstating the border would be a mammoth task.

Traffic of goods without border controls

The BBC calculated that there are some 270 border crossing points along the 500-kilometre border. That is more than twice as many as the longest border in the world - nearly 8,900 kilometres - between the United States and Canada.

Proposals by various British politicians on how to supervise the traffic of goods with means other than border controls - for example, using technological equipment - all break down on the fact that they wouldn't work without the cooperation of importers and exporters. Those who do not properly declare their goods can't be documented.

Yet, even should Britain depart the EU on March 29 with an agreement, it will only mean a postponement of the question about how a border can be prevented.

Should London, as announced, leave the European customs union and the EU single market, there would be no other alternative to border controls.

This is the reason given by Brussels and Dublin for pushing for the backstop deal that London hates.

Under this arrangement, Britain would remain entirely in the customs union and allow Northern Ireland in part to remain in the single market until some bettersolution is found.

But there are now fewer than seven weeks left until then, and the fronts have hardened, both within the British parliament, and between the British government and Brussels.

What happens next is anyone's guess.

Rita Gallagher, the 87-year-old mother of Pettigo store owner James Gallagher, who is still working the cash register, points to the dilapidated barracks of a former control post on the other side of the street. "They will open up the border post again," she predicts.