Residents of Curtis House in New Southgate regarded Muktar Said-Ibrahim and Yasin Hassan Omar as feckless young men living aimlessly on state benefits.

Ibrahim had served time in Huntercombe Young Offenders’ Institution, Oxfordshire, according to Whitehall sources, and Omar, was known as a shoplifter.

As children, both fled civil war and bloody conflict in Eritrea and Somalia for the safe refuge of Britain. Yet they came to hate their adopted homeland so much that they volunteered for suicide bombing missions.

In preparing for “martyrdom” Ibrahim, 27, and Omar, 24, had turned the tower block that they shared with hundreds of people into a terrorist safe house and a bomb factory. Forensic science teams have found traces of explosives in flat No 58 and the rubbish chute as well as a substantial cache of bombmaking chemicals in a lock-up garage.

Tanya Wright, who lives on the floor below Omar’s rented flat in Curtis House, said that she saw both men on Friday afternoon, the day after the failed bombing attempts. “I saw them acting suspiciously outside their flat,” Miss Wright said. “As soon as they saw me they jumped back in the flat and shut the door. They looked shocked and panicked.”

She has given a statement to police who are increasingly concerned that, having failed in their missions, Ibrahim and Omar returned to rearm and try again.

The would-be bombers both arrived in Britain as refugees from Africa. Omar, a Somalian, arrived in 1992, aged 11. He is thought to have spent most of the next seven years in foster care. He was granted exceptional leave to enter Britain for four years. That was extended and in May 2000 he was granted indefinite leave to remain, entitling him to live permanently in Britain. He has been able to work legally since he was 16.

Ibrahim, also known as Muktar Mohammed-Said, was given exceptional leave to remain in Britain in 1992. He had arrived with his family from Eritrea. In November 2003 he applied for British citizenship which was granted, with a passport, last September.

Ten months before he tried to blow up a No 26 bus in Hackney, East London, he swore an oath of allegiance, stating that he would be “faithful and bear true allegiance to Her Majesty Queen Elizabeth the Second, her Heirs and Successors, according to law”.

There was growing concern in Whitehall last night over how he had made a successful citizenship application despite having a conviction.

Ibrahim was once a criminal gang member jailed for violent muggings, it emerged last night. A year after leaving school, he was arrested in Royston, Hertfordshire, after a street robbery. Members of the gang were jailed at Luton Crown Court in 1996 for terms ranging between two and four years after admitting five robberies in the Welwyn Garden City and Stevenage areas. Ibrahim received five years because he had been carrying a knife.

Ibrahim also committed crimes in Letchworth.

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