“Euro = Pound” says a sign in the Jack and Jones shop in one of Newry’s new shopping centres. The manager, Darren Carlon, put it up last week. If you buy a £60 jacket you can choose to pay €60 instead, and save 10%. Doesn’t he lose money this way? “No,” says Carlon. “We have higher traffic from southern Ireland – and hope to sell more.”

The shopping centres in Newry in Northern Ireland are only a few miles from the border, and at the moment they are seeing an influx of shoppers from the Republic. The decline of the pound after the EU referendum makes buying things there cheaper.

“We thought Brexit would kill us, but in fact it’s quite the opposite,” says Paul Morgan, the manager of the Home Trends shop in the same shopping centre. He is attaching a new best price sign to one of his carpets and is delighted. Four out of 10 customers came from the Republic of Ireland this year, he says. Last year, it was just 2%.

On the other side of the border, in Dundalk city centre, Gerard McEvoy’s department store is also busy. “I can’t see a big difference compared with last year,” says McEvoy, who employs 27 people. “We are situated in the city centre. People come here and shop anyway.”

But McEvoy is worried about the consequences of Brexit, and not just because of his business. He lives in Northern Ireland and remembers the Troubles. Like every local born before 1990, he can recall the daily checks when he crossed into the Republic, as well as the atmosphere of oppression. “It could come back easily,” he says.

After Brexit, the EU border will go across the island of Ireland. According to the Schengen agreement, the Republic will be obliged to introduce border controls. Could the peace process be endangered?

Declan Kearney, the Sinn Féin national chairman, is firm. Checkpoints? “Absolutely not,” he says. “The peace process was about breaking down borders. We are not under any circumstances going to stand by and allow a non-democratic decision taken in England to create a whole new division on the island of Ireland, with political and economical consequences.”

He warns: “I think the peace process is irreversible, but it can’t be taken for granted.”

At the moment a hard border is difficult to imagine. Travelling on the motorway from Dundalk to Newry, you can only tell you have crossed it when the kilometres on the road signs turn into miles.

People in Newry and Dundalk describe a past full of mistrust and terror, with the constant soundtrack of helicopters. “We had the hardest of hard borders here,” says Conor Patterson, who grew up in Newry and runs a business development agency. He speaks for the Newry Chamber of Commerce when he says: “A border between here and Dundalk will be a disaster.”

Paddy Malone, who grew up in Dundalk and is an active member of the Chamber of Commerce there, shares his conviction. Both are campaigning at every opportunity, whether in the House of Commons or the French parliament, for the border to remain open, not only for the sake of the retailers and shoppers but for the whole region.

Both Newry and Dundalk were prosperous in the 1920s and experienced a decline after the division of Ireland. They were neglected by their governments in the 1970s and 80s, but had a remarkable upswing in the 2000s. The benefits of the EU, as the border ceased to be a barrier to the movement of goods and people, helped both cities enormously, as Patterson and Malone independently stress.

They attracted international companies such as Paypal, which has an office in Dundalk, and local firms also grew, providing skilled jobs on both sides of the border.

You can drive between the two in half an hour, whereas in the days of border controls, Malone points out, it took a lorry an average of four hours.

“We need to send the message out to the British government as well as to Brussels: when you are talking about Brexit you can’t just think of little England. There are not only a million people living directly along the border but over 6 million people living on this island. All of them will feel any change of Britain leaving the EU. It will have an impact on the whole of Ireland,” he says.

No one in Ireland wants the border back. Not the locals, not the commuters, not the business people. And certainly not the shoppers.