Would-be suicide bomber Muktar Said-Ibrahim is a convicted violent criminal who was part of a teenage gang which carried out a string of muggings.
Friends said that as a youngster he smoked cannabis and was known as a troublemaker but he was radicalised in jail.
He was sentenced to five years in early 1996 but qualified for early release after serving two-andahalf years at Huntercombe Young Offenders' Institution and Woodhill Prison. When he came out he adopted Islamic dress and became devout.
Police are looking into whether he attended the Finsbury Park or Brixton mosques in London and whether he met shoe bomber Richard Reid.
Said- Ibrahim had arrived in the UK from Eritrea in east Africa as a refugee with his family in 1992 when he was 14. He attended Canons Hill school in Edgware.
In November 2003 he applied to become a British citizen and he was given a British passport last September.
A condition for naturalisation is being of "good character" and the Home Office was unable to comment on how Said-Ibrahim obtained a passport despite a criminal record.