The boy – who does not speak verbally – disappeared from a mental hospital in Kent on April 7 under the Mental Health Act. Two days later, he was arrested by the British Transport Police (BTP) in Euston on suspicion of tax evasion, before being detained by the Immigration Service near Gatwick, although he was British. “It’s just awful,” said the boy’s mother. “Because he is black, they just assumed, ‘Let’s pick him up and put him in a deportation center.’ When the boy returned to the hospital, his clothes contained Interior Ministry documents that incorrectly stated his name and date of birth and recorded his nationality as Nigerian. “How do they know he’s from Nigeria when he doesn’t even speak to them?” said the woman about her son. When the hospital was informed of his disappearance, the family, local police and the BTP were notified, the woman said, and was reported missing. It is not clear where the boy went in the days before his arrest. He appears to have traveled to Manchester, where the family previously lived, before attempting to return to London without a telephone, money or ID. On the morning of April 9, BTP said it had been notified of a fare break on a train bound for London from Manchester. In a statement, BTP said the man gave a fake name and date of birth, saying he was 20 years old. In Euston, he was arrested as a suspect in a fare escape and was arrested by police in Islington, according to BTP, where “officers were unable to contact the man or verify the information provided despite their efforts, which included a presence at the address given “. The boy’s fingerprints were then taken and he was arrested by the Immigration Service. Documents apparently prepared at the detention center seen by the Guardian incorrectly state his name and date of birth and state his nationality as Nigerian. He is described as a person who requires permission to enter or stay in a country he does not have. In a document, he said his departure from the UK was “imminent” as he had not given “satisfactory or credible answers” to immigration officers. The boy is a British citizen and has never left the United Kingdom. His mother said he could not say his date of birth correctly and would never say he was from Nigeria. This week, a BTP commander told her that when they searched Kent for the boy’s address, they found a Nigerian family living there. She was told that police found out that the boy was of Nigerian descent as he had the same accent as the locals. She challenged this statement, describing her son’s pronunciation, when he rarely speaks, as Mancunian and London. James Wilson, deputy director of Detention Action, which works with deportees, said unaccompanied minors or children under the age of 18 should not be detained from the outset. “Theoretically, booking should be the ultimate solution, rather than an early step you would take,” he said. A spokesman for the Interior Ministry said: “We rely on the information provided by our police partners when a person is referred to the Immigration Service. In this case, the person stated that he was an adult man in the British Transport Police. “The police nurses evaluated him and did not pose any physical or mental health problems.” The spokesman said that the person did not give more information to the Immigration Enforcement Service and as soon as his true identity was established, he returned to the care of the mental health services. BTP said it was investigating the incident internally.