UK ports on Monday sailed through the first working day since Britain left the EU's single market and customs union, with preparations for post-Brexit trade holding firm as traffic remained muted.

The country embarked on life outside the European Union late Thursday but with the light holiday season traffic, there has so far been little sign of long-feared disruption.

The government and many logistics operators have feared teething problems as officials on both sides of the Channel implement new customs systems after decades of frictionless trade.

At Dover in southeast England, Europe's busiest port for roll-on, roll-off freight and where more lorries were expected to make continental crossings Monday, traffic remained light but free-flowing.

"We're quite happy with how it's gone... the vast majority of freight traffic have a green light to go," Chris Parker, of DFDS -- one of two ferry companies operating services from the port to northern France -- told BBC News.

The UK government is concerned that truckers will turn up at Dover without the proper paperwork, causing delays
The UK government is concerned that truckers will turn up at Dover without the proper paperwork, causing delays AFP / JUSTIN TALLIS

"As we expected, the traffic's been much less than last year," he said, noting freight was always quiet in the new year and expected to build up again "over the next week or two".

A DFDS spokeswoman said its cross-Channel traffic through Dover in the first two days of 2021 was down by more than half on last year.

Figures from port officials confirmed the freight reduction in recent days, with 2,237 lorries passing through Dover on December 31, falling to just 673 on New Year's Day and 914 on Sunday.

"Traffic has continued to flow smoothly through the port since the Brexit transition (ended)," a port spokesperson said.

Authorities aim to avoid backlogs similar to one created late last year when France closed its border owing to fears over a new variant of the coronavirus
Authorities aim to avoid backlogs similar to one created late last year when France closed its border owing to fears over a new variant of the coronavirus AFP / BEN STANSALL

EU-bound lorry drivers must now carry a slew of new paperwork, and those using Dover must get a Kent Access Permit prior to setting off to show they have all necessary documentation.

Cameras will identify any trucks without the permit, and drivers face fines of up to ?300 ($410, 334 euros) for entering the county without one.

The government, which has employed 1,000 new border officials, devised the permit over fears that lorries could turn up at Dover without the proper paperwork, causing delays in and around the port.

In a sign of the chaos that could be possible, thousands of trucks were stranded in Britain before Christmas after France closed the border in response to a new coronavirus variant.

Lorry drivers who have not done the necessary paperwork are to be directed to a dedicated site near Dover
Lorry drivers who have not done the necessary paperwork are to be directed to a dedicated site near Dover AFP / BEN STANSALL

Ministers believes most large businesses are ready for the new regulations but that around 50 percent of medium and small firms have not carried out the measures now needed to export goods to Europe.

Meanwhile to help ease potential backlogs of incoming lorries in the next few months, they have opted to phase in verification of imports, with full checks on goods only from July.

Romanian trucker Alexandru Mareci, one of the first to enter Britain Friday after the new rules kicked in, returned to the continent with an empty truck the following day.

Although he had never heard of the Kent Access Permit, Mareci said leaving the UK went smoothly.

"Paperwork was made by (our) office in Spain, everything is online now, they just send us a QR code," he told AFP, referring to a digital barcode that can be displayed on a smartphone.

Britain voted to leave the EU in 2016, and formally left in January last year, ending nearly 50 years of integration in the European project.

As part of the divorce deal, it remained bound by most of the bloc's rules until December 31, while talks took place to agree the future trading relationship.

London and Brussels finally struck a last-ditch deal on Christmas Eve, which assured no tariffs and quotas on trade.

However, not everybody has adapted to the new system seamlessly.

Loch Fyne Seafarms in Scotland complained the rules were an "absolute mess" and Brexit a "national embarrassment" after it was unable to complete the new bureaucracy on Monday, which is a Scottish national holiday.

"For the first time in nine years, we've been unable to export our products to the EU," a company employee said in a video posted on Twitter.

"It's put us in a very difficult position, that we've already been in over the last few months with the coronavirus and the problems at the border over Christmas.

"So it just keeps getting worse."