Many unaccompanied children who have fled Afghanistan and had their asylum claim rejected in the UK are given until they are 18 before being sent back. For the past seven months the BBC has followed some of these young men. They face life in an unfamiliar and dangerous country, write Chris Rogers and Sue Clayton.
Najib makes his way nervously through the streets of Kabul. At 20, he is alone in one of the most dangerous countries in the world.
On every corner heavily armed solders guard communities and government buildings. It is a city on the edge - there has been a surge of Taliban attacks in Kabul in recent weeks. "You can see it's dangerous," he says as army helicopters fly low across the city skyline, "It is getting worse here. There are bombs and explosions everywhere."
As an Afghan, you might expect Najib to be used to the Taliban violence, but the city is as strange to him as it would be to any foreigner.
He spent much of his childhood in the UK. Originally from Lashkar Gah, the capital of Helmand province, when his father and brother went missing his mother arranged for him to be got out of the country by agents. He spent months on the journey including walking through the mountains between Pakistan and Iran.
But Najib was deported by the Home Office back to his country of birth two years ago.
"I don't belong here, I wasn't educated here and I don't know the culture. Britain is my home," he says in a strong Midlands accent. Najib still sports a hairstyle that wouldn't be out of place on David Beckham and is wearing a trendy shirt, jeans and trainers.
He couldn't look more British, but he says that is a problem. "The Taliban attack the West here, people who work for the British government or even people who just come from Britain and America, It is dangerous here."
He looks on at the hopelessness around him - dozens of war widows are begging for money and food on their knees, while gangs of young Afghan men scrape a living offering their labour on street corners. There is 40% unemployment in a country struggling to recover from an endless war, and Najib wants out.
"I will leave Afghanistan and go to another country as a refugee," he says. "There is nothing for me here. Even if I get sent back I will just keep trying to leave Afghanistan."
Najib later jumps on to a bus out of Kabul with just a rucksack of belongings. He is heading to the border and plans to make his way back to Britain with the help of traffickers. It's the same 4,000-mile journey he made as an 11-year-old boy.
Since 2006, 5,500 unaccompanied Afghan children have reached the UK and claimed asylum. More than 80% of those who claimed persecution by the Taliban had their cases rejected.
But rather than send them straight back, the Home Office offers them a temporary life in Britain, usually with a foster family until the age of 18, when they must leave the country voluntarily or be deported.
The vast majority of the Afghan children who come to the UK are male. Families believe their daughters are too vulnerable to be sent alone on the path to Europe.
Najib spent most of his childhood in Southam near Leamington Spa with foster parent Linda.
"It was wrong to send him back, they are just pawns in a political process," she sobs as she flicks through an album of photos showing Najib's first day at the local school and the Christmases and birthdays they shared together. "He is a number so that anybody who wants to get political gain can say, 'We have sent this many people back'.
"How can they justify sending someone to a country they hardly remember when they have made a life for themselves here?"
Another former child asylum seeker placed in Linda's care faces deportation any day now. Faisal, now 19, can appeal against his deportation, but he is taking no chances after seeing what became of Najib. He has been in the UK since he was 14.
In a tower block several miles from his foster home, Faisal is making a bed on the floor of a friend's flat. He has gone on the run, moving addresses every few days. "I'm so scared the Home Office are going to pick me up," he says as he heads out on to the balcony, scouring the streets below. "I check for them every 20 to 30 minutes during the night. Early in the morning I'll leave and go and sleep somewhere else."
According to research by the Bureau of Investigative Journalism, the Home Office has deported more than 600 failed child asylum seekers to Afghanistan since 2011. Nearly 500 more are earmarked for removal. Yet the government advises its own citizens not to travel to Afghanistan because of the threat of terrorism and kidnapping.
In a statement, the Home Office says it is proud of its history of giving asylum. "Where people establish a genuine need for protection, or a well-founded fear of persecution, refuge will be granted. Every case is carefully considered on its individual merits."
Refugee campaigners accuse the Home Office of effectively warehousing Afghan children - dismissing their claims of persecution in Afghanistan with the sole intention of deporting them when they become adults - to keep migrant numbers down.
Juliette Wales, of Kent Refugee Network, has tried to help hundreds of young Afghans appeal against their deportation. "It's tragic to see these kids who believe they are safe, working really hard and going to college, turn 18 years old and turn into the state they turn into, it's a waste of life."
Many of the former child asylum seekers we met are convinced they will be killed by the Taliban in Afghanistan, but their greatest fear is often losing the life they have made for themselves in Britain.
Nasser, 23, says he enjoyed a typical British upbringing in North London for eight years. He had a girlfriend, a network of friends and had completed his studies.
When we found Nasser in a small, dirty, rented room on the outskirts of Kabul, he had been deported just four days before. "I am not happy here. I feel like I am going crazy here. What am I doing here?" he asks, clearly shell-shocked to be back in a city he hasn't seen since he was 11.
He says that in the chaos of war he lost touch with his family. "What am I going to do here by myself, alone?" he says.
He is terrified and hasn't left his room since he arrived. "In this country how am I going to make a life? I can't go outside. I can't go outside in case of a bomb by the Taliban, and I am scared something is going to happen. This is our life, and it's not a life."
The Home Office does not monitor what becomes of deportees once they arrive in Kabul, but human rights campaigners do. According to a study of 200 failed child asylum seekers, they tend to turn to two options - escape Afghanistan by fleeing back to Europe, or escape reality by taking drugs.
Under a notorious bridge on the River Kabul, where a community of around 300 heroin users live in stream of rubbish and sewage, we find 23-year-old Ahmed. He claims he lived in Manchester for eight years - he's been back in Kabul living with his mother for 18 months.
"This is not a situation I am proud of. Today I promised my mother this would be the last day I take drugs," he say. But he admits it's a promise he has made many times.
"It eases the pain, this is my escape, I had a life in Manchester, but not here. I pray to God to get me out of this situation."
His thin, dirty face and soulless eyes suggest months of drug abuse, and he's not ready to quit escaping reality just yet. He waves goodbye as he makes his way back under the bridge for his next hit.
Chris Rogers reports for Our World: Deported to Afghanistan broadcast on the BBC News Channel on 18 and 19 July at 21:30 GMT. It will also be broadcast on BBC World News on 17 July at 23:30 GMT, 18 July 11:30 and 22:30 and 19 July at 17:30. You can catch up via the BBC iPlayer
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