Construction has begun on a four-metre high concrete barrier aimed at stopping migrants targeting vehicles around Calais.
The barrier - dubbed The Great Wall Of Calais - will run for nearly a mile along the main motorway to Calais and is being paid for by British taxpayers.
The wall is being built within a few hundred metres of the so-called 'Jungle' migrant camp, which is now thought to house more than 10,000 people.
It has been reported that it will cost £1.9m to build, and it is intended to add another layer of protection against attempts to stow away on vehicles as they approach the port heading for Britain.
It is due to be completed by the end of the year, replacing the wire fences that are already there.
Britain's Immigration Minister Robert Goodwill unveiled the plan to build a "big new wall" earlier this month.
But the UK's Road Haulage Association attacked the idea, saying it would be a poor use of taxpayers' money.
Some migrants try to get vehicles to slow down on the motorway, by creating makeshift roadblocks, and climb aboard in an attempt to reach the UK by ferry or Eurotunnel services.
"This wall is going to prevent migrants from getting onto the road every night. They put tree trunks, branches, gas cylinders" in the road, Calais port chief executive Jean-Marc Puissesseau said earlier this month.
"We can no longer continue to put up with these repeated assaults."
Children
Construction began as Britain's anti-slavery commissioner warned that children from the 'Jungle' were risking their lives every night in an attempt to reach the UK.
In a letter to UK Home Secretary Amber Rudd, Kevin Hyland said not enough is being done to "address the vulnerabilities of migrants, in particular unaccompanied children".
"Children are not waiting," he wrote. "Every night they go to their smugglers who have promised to get them across the Channel. Every night they think that this time they will be lucky.
"However, every night each of these children are at risk of exploitation and sadly even dying as they take huge risks to reach the UK."
Statistics from the camp suggested that there were 865 children living in August, 676 of them unaccompanied.
A spokeswoman for Britain's Home Office said: "Over 120 cases of unaccompanied children in Europe have been accepted for transfer to the UK under the Dublin Regulation since the start of the year and we want to build on this progress."
