Night has fallen over Calais and Muhammed’s long wait is finally over: he warms his hands over a small campfire one last time, wraps a blanket tight around his head for warmth and walks towards a barbed wire fence separating him from railway tracks leading to England.“In fifth grade, we learnt about Africa,” says the 31-year-old. “Then we learnt about the world, about England and about democracy. England is a good place.”

Migrants such as Muhammad have been passing through the northern French port for years, viewing it as the penultimate stop of a journey that typically spans thousands of miles, often in perilous conditions.

But this week Britain has resembled a fortress desperately trying to keep out thousands of migrants from Africa, the Middle East and beyond attempting to overwhelm the defences of the Channel tunnel by sheer force of numbers. On Monday night, 2,000 people stormed the tunnel site trying to jump on to trains bound for the UK. Another 1,500 tried again the following night; one man was killed by a lorry as he crossed a road.

Britain and France have pledged additional security measures and police to protect the tunnel. But Christian Salomé of L’Auberge des Migrants, which provides basic aid to the migrants in Calais, says it will only push them to take even greater risks. “This is not security,” he says. “It just makes it more dangerous for them to cross.”

In the meantime, the cost to business is rising: the disruption in Calais is estimated at £250m per day in lost trade for UK businesses cut off from a vital transport artery.

Like Muhammed, who came from Ethiopia, most of the migrants in Calais are on a one-way ticket, fleeing from war and violence back home. Kamel, a robust 28-year-old wearing a baseball cap and a “Harvard”-stamped T-shirt, left his native Syria six weeks ago after his mother was killed in fighting and his home was destroyed.

He says he spent a total of €8,500 to get to Calais, paying different people on a journey through Turkey and Greece that included a hazardous two-day trek through the Serbian mountains before reaching Austria and Germany.

But most migrants from Africa travel through Sudan and on to Libya before paying more than $1,000 to be crammed into a small boat that transports dozens of people at a time to Italian shores.

Struggling to feed a small fire in a wooded area near the tunnel entrance, Kamel says that his 15 failed attempts so far to reach the UK have done nothing to deter him. “I’ve come too far and spent too much to go back now,” he says. “Anyway, there is nothing to go back to.”

His obsession with England is typical of the vast majority of migrants in Calais. They say that seeking asylum is relatively easy and quick in the UK compared with France or other EU countries.

They also say that it is easier to find informal work — in part because the economy is growing but also because there is no ID card requirement. Besides, most speak at least some English, which makes the UK their natural destination.

Not everyone leaves, though. For the past three months, Mohammad Ali, a 65-year-old Afghan former school teacher, has holed up in Calais’s notorious “jungle”, the 18 hectares of dusty scrub land where an estimated 2,000 migrants now sleep in makeshift shelters.

Fleeing from fighting in Afghanistan, where he left his wife and eight children, Mr Ali had his gaze fixed on Dover. But he now thinks it may be too dangerous and is considering applying for asylum in France instead. “I don’t like the risks you have to take to get across,” he says. “I am not going to commit suicide for this dream.”

There are increasing signs of permanence in Calais’s jungle, which is carved into national groups — Sudanese, Ethiopians, Eritreans and Afghans — like a miniature map of global human conflict. On one side, Eritreans have built a church — complete with a cross-topped spire — from wood and polythene.

Afghans such as Mr Ali pray five times a day in a mosque covered in green plastic sheeting. Inside its dark interior, a small group of migrants lie asleep on carpets while another stacks copies of the Koran in the corner.

For the great majority, however, staying in Calais seems about as desirable as returning home. Mahammed, a 19-year-old from Sudan, says that it has taken him a year to near the end of his journey. His 10 failed attempts have ended in beatings by the police, being pepper sprayed and dumped miles from Calais, he says.

But none of that has quelled his drive to get to England, where he says he wants to finish school — a promise he made to his subsistence-farmer parents back home. “English is my favourite language,” says Mahammad. “I am never giving up.”