The flag of Britain’s biggest trade union, Unite, was brandished at a migrant demonstration in Calais

The flag of Britain’s biggest trade union, Unite, was brandished at the Calais demonstration which led to the storming of a British ferry, newly uncovered footage reveals.

The subsequent flashpoint when the Port of Calais was invaded by hundreds of migrants and anarchists came just hours after Labour leader Jeremy Corbyn’s visit to migrant camps in Dunkirk and Calais last week.

The video shows the Unite banner, along with countless Stand Up To Racism placards, being held aloft as the 2,000-strong group made their way from the ‘Jungle’ camp outside Calais into the town’s main square.

It also reveals the disastrous blunder by French police which allowed the demonstrators access to the unguarded port.

Among the mainly Kurdish and Afghan demonstrators were a small number of Westerners, some of whom were believed to be anarchists from the No Borders group, which backs the pro-migrant demo.

Just how the Unite symbol came to be at the march is a mystery.

The union – the Labour Party’s biggest backer – has made it clear it equates anti-immigration views with racism, but has not previously backed the calls of Calais migrants to be admitted to the UK.

The red Unite flag was first seen last Saturday carried by a man clad in black who had masked his face to prevent identification.

Beneath it fluttered the orange standard of Right To Remain, a UK-based human rights organisation.

At one point in the march, the house of a Frenchman believed to be associated with nationalists in Calais, was besieged by the mob and various items such as bicycle tyres were thrown at the family as they tried to reach safety.

The migrants continued marching through Calais with loud hailers, then the defaced statue of General de Gaulle in the town centre is shown in the video.

People marched from the 'Jungle' camp, pictured, and into the Port of Calais where they caused havoc

After a short stand-off with police, the group are inexplicably allowed entry to the seafront and then to the Port of Calais where they have ample time to rip off a section of the perimeter grille and swarm into the port, some of them making it on to the P&O ferry Spirit of Britain.

Police in riot gear arrive hopelessly late, drop a tear-gas grenade near the breach in the fence which has little effect, but after about 90 minutes they round up the migrants and march them out.

Unite said last night its involvement was ‘not nationally organised’ but some of its members had been ‘acting of their own initiative’ and in the traditions of a movement that has never turned its back on people in need.

Protest: Migrants with placards storm towards the port of Calais during a demonstration in the town centre

French riot police said officers ‘had reacted to a fraught situation which extended across the whole of Calais’, and that they reacted accordingly ‘while ensuring public safety’.