CALAIS, France - Moments after Britain completed its divorce with the European Union, the first trucks hauling goods across the new customs border presented their clearance documents to French agents before loading onto a train to pass through the Eurotunnel.

A barcode on Romanian driver Toma Moise's paperwork was scanned and approved in seconds. "The future, I don't think it will be difficult," he said in broken English before continuing his journey towards Britain.

Cast as the dawn of a newly independent "global Britain", its exit from the world's biggest trading block means the return of customs formalities on the island nation's frontier with Europe for the first time in several decades.

Freight flows through the Eurotunnel's Calais terminal were extremely light in the early hours of the New Year.

British and European businesses have warned of carnage at the border as they learn to navigate a wall of red tape and paperwork that threatens to disrupt the smooth flow of nearly 1 trillion euros in annual trade.

Yann Leriche, chief executive of Getlink which operates the Eurotunnel, told Reuters tweaks to customs procedures might be necessary but that there would be no chaos in the weeks ahead.

(Reporting by Richard Lough; Editing by Daniel Wallis)