The problem is not where Mr Biswas has come from, but where he is going to. His fields lie 60 miles east of Calcutta, right in the no man’s land between India and Bangladesh.

Next month India plans to fence off this area of West Bengal as part of a little-known £600 million project to erect a steel barrier right along its 2,500-mile border with its much smaller Muslim neighbour. As a result Mr Biswas and his village of 2,000 people will be sealed off from their own country.

“We’ll be fenced out of India,” the 30-year-old farmer complains. “What if there’s an emergency and we have to go to the mainland? What if there’s no one at the gate to let us out? We’ll be completely cut off.”

India is 30 times the size of Bangladesh and the two nations share South Asia’s longest border. But despite India’s help during Bangladesh’s War of Independence in 1971 against what was then West Pakistan, relations between the two countries have deteriorated in recent years.

While the world’s attention has been focused on the Israeli security barrier sealing off the West Bank, India has been building a far longer fence to keep out Islamic militants, thwart cross-border smuggling and stop human trafficking.

More than 1,300 miles of the barrier has been erected in the six years since building began. Snaking through jungles, rivers and the villages of five states, Delhi’s floodlit, 12ft double fence packed with razor wire will render India a fortress against her neighbour.

The problem India faces is that 100,000 of its citizens live and farm on a 150-yard patch of land hugging the international border known officially as “the zero line”, and they live on the wrong side of the fence’s designated path.

Entire villages, including schools, temples and mosques lie in what will effectively become no man’s land. Although Bangladeshis and Indians along the border have lived cheek by jowl for decades, and share the Bengali language and culture, relations between them are strained by suspicion.

The Indian villagers fear that once the fence is built they will be harassed by Bangladesh’s security guards. They say that locked away from Indian guards their fields and homes could be looted with impunity by Bangladeshi farmers.

Rabreya Bachhri, who lives in Jayantipur, the same village as Mr Biswas, says: “Even now the Bangladeshis cross over at night from their side and steal our cooking utensils and cows. We’re very worried about our future. India has to look after us and keep us inside the fence or it will make us Bangladeshi.”

Sandwiched between two nations, the villagers say that they get a raw deal from both countries. The Indian and Bangladeshi security forces accuse them of colluding in smuggling and illegal immigration.

Officers from India’s Border Security Force say that Bangladeshis claim they are entering India for medical treatment but do not have the required travel documents. One senior officer said: “Even those who come with documents don’t go back. The number of people coming into India is less than the number returning.”

Officials say that the fence has already stemmed the flow of illegal Bangladeshi immigrants attempting to cross into India from about 65,000 annually a decade ago to just 10,000 this year.

Shivajee Singh, a border security force inspector-general, said: “When the fence was put up the numbers came down.”

But Delhi is increasingly concerned about infiltration by militants from a country with a large, poor Muslim population that was scooped from India by partition. It accuses Bangladesh of harbouring insurgent groups fighting for accession from India from its northeastern states of Assam, Tripura and Manipur.

There are also concerns about the rise of radical Islam after the spate of bombs and violence in Bangladesh. “Militancy is a new dimension,” Mr Singh said. “Earlier people came for employment. Now we’re getting reports that they’re coming for terrorist activities.”

India has consequently accelerated the barrier’s construction, hoping to complete it by spring next year. It will also increase the number of troops along its border with Bangladesh from 45,000 to 53,000. In a move to bring villagers such as Mr Biswas inside the barrier, India has asked Dhaka to permit it to build the fence within the zero line, an area that both countries promised to keep free from defence structures in an agreement made 30 years ago.

Delhi claims that its request has so far been refused. However, a senior official of the Bangladeshi Embassy in Delhi said that talks between the two nations were continuing. “We’re always open to discussion with friends and neighbours,” he said. “But the agreement can’t just be changed by wishful thinking.”

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