As the UK braces for the end of the Brexit transition period, the Northern Irish town of Warrenpoint reflects on four years at the heart of Britain’s turbulent departure from the EU.

A port hub humming with ferries and freight, Warrenpoint sits on the Irish border and was the site of the deadliest attack on British troops during “The Troubles”.

Since the 2016 vote to leave the EU, all those elements became shuffling pieces in the intractable puzzle of Britain’s bid to split with the bloc.

Mark Kelly, the head of the town’s chamber of commerce, said: “Unfortunately we are very much in Warrenpoint right at the centre of a whole plethora of issues, historic and recent, around Brexit.”

As co-owner of a hardware wholesaler stocking around 70 per cent of goods from the EU, he has spent more time than most musing on the future after January 1.

On that date, the Brexit transition period freezing EU-UK relations will end and the full effect of the split will be felt.

Kelly said: “We just have to make the very best of it.”

Britain voted to leave the EU in June 2016 but talks between London and Brussels immediately stalled over the thorny issue of the Irish border, which bisects the estuary of Warrenpoint.

The 500km boundary between Northern Ireland and EU member state Ireland was largely dissolved as a sectarian conflict known as “The Troubles” wound down.

But up until 1998, some 3,500 were killed by bombs and bullets as unionists, republicans and security forces battled over the destiny of the British province.

The border was a flashpoint in killings, and there were fears that resurrecting infrastructure to police the new frontier of the EU could unravel a fragile peace.

In Warrenpoint, those fears were freighted with a dark significance.

On August 27, 1979, two Irish Republican Army bombs killed 18 British soldiers at “Narrow Water”, which marks the border – the deadliest attack on troops in the conflict.

Outside the town, the spot remains marked by a rank of well-tended poppy wreaths.

“Northern Ireland has been in the eye of the Brexit storm since the very start,” explained Jane Morrice, the former head of the EU commission in Northern Ireland.

Morrice – also an architect of the 1998 “Good Friday” peace agreement – said “there was not an understanding among the majority in Great Britain [England, Scotland and Wales] of the impact the border would have on these discussions”.

Eventually, a deal was sealed for the UK and the EU to split, keeping the border open by aligning Northern Ireland to the bloc’s single market and customs union.

The dark prospect of a hard Irish border has been avoided but for Warrenpoint, the changes will still be dramatic.

Warrenpoint’s port – the second busiest in the region – will soon be a de facto EU-UK border as checks which would have been needed at the Irish border take place here instead.

At the town-centre office of freight forwarding firm Trans Europe Express, there is a steady roar of passing lorries loaded with shipping containers.