Hundreds of trucks roll off the docks at Holyhead every day, bringing goods to and from Ireland in an economic lifeline for this deprived corner of Wales, which is now threatened by Brexit.
Just 73 miles (117 kilometres) from the Irish capital Dublin, the port’s future will depend on how any Brexit deal affects two borders – the one between EU member state Ireland and Britain and the one between Northern Ireland and mainland Britain.
The concern for many here is that companies will start finding alternative trade routes for goods travelling between Ireland and continental Europe to avoid Britain after Brexit.
With negotiators still at loggerheads in Brussels ahead of a key EU summit on Wednesday and Thursday, concern about increased checks is already forcing some companies to change tack.
Ray Cole, transport director at Virginia International Logistics, said his company was already using the service from Dublin to Cherbourg in France ‘whenever we can’.
The cost for Holyhead, Britain’s second biggest roll-on/roll-off terminal after Dover and an area that voted narrowly to leave the European Union in the 2016 referendum, would be high.
‘The problem that we have, it could affect jobs,’ said Michael Hartnett, a 50-year-old Irish truck driver. Port users had ‘zero information’ about what Brexit deal to expect, he added.
The port sustains 650 jobs directly, according to Carwyn Jones, a councillor on the island of Anglesey where Holyhead is located.
Jones said the port was ‘absolutely crucial here to us’.
At three-and-a-half hours, the link is the fastest between the Republic of Ireland and Britain, making Holyhead a key hub for major industries such as agri-foods, automobiles and medicine.
‘Absolute chaos’
The terminal is located next to the windswept, grey streets of Holyhead town, home to around 12,000 inhabitants.
The comings-and-goings of ferries, about twenty times a day, are the only moments to disturb the quiet.
At those times, dozens of trucks queue to board or disembark and continue their journey to the rest of Britain or the continent.
‘If on Day One of Brexit the lorries have to queue, it will cause chaos, absolute chaos, bring this island to a standstill,’ warned Jones, a member of a Welsh nationalist party.
Labour MP Albert Owen said that even a delay of 15 minutes could create a line of trucks stretching back five kilometres.
‘The port doesn’t have the capacity for that,’ he said. 
A new route directly linking Ireland with mainland Europe and bypassing Britain is under consideration, with the European Commission floating Zeebrugge in Belgium or Rotterdam in the Netherlands as potential beneficiaries.
Another risk highlighted by the Welsh Assembly is that any deal in which the British province of Northern Ireland remains in regulatory alignment with the EU could reduce the amount of traffic Holyhead handles to and from the province.
Instead of transiting through Dublin and undergoing customs checks on arrival at Holyhead, operators would likely ship directly from Belfast to the English port of Liverpool.
Around a quarter of the goods that pass through the port either originate or end up in the British province of Northern Ireland.
Howard Browes, owner of the Beach Hut restaurant and hotel opposite the port, said: ‘Obviously everyone is very apprehensive… as to where the border is going to be drawn’.
‘There will be an opportunity’
With only five months to go until Britain leaves the EU on March 29, other local businesses are also becoming concerned.
‘It could possibly have a very adverse effect on business in Holyhead generally, not just on my business,’ said Joe Caffrey, a retired police officer and owner of the Manroven guest house.
Ferry company Stena Line, operator of Holyhead port, told AFP that it will ‘analyse the situation’ and ‘review our business accordingly’ once the final situation becomes more clear.
But Nicholas Whatmore, general manager of RoadKing, which owns restaurants for truck drivers that include laundry and other facilities, said he saw Brexit as a chance.
A border would signal the return of duty-free on ferries and Holyhead could become a ‘fantastic’ booze cruise destination, he suggested.
Putting his money where his mouth his, Whatmore’s company is investing £5 million ($6.5 million, 5.7 million euros) in the local area to fund a hotel and a service station.
‘Where there will be a down-turning business, there will be an opportunity somewhere else,’ he said.