A Nigerian man closely linked to a group of British Islamists has been stripped of his British citizenship over fears he was planning a Paris-style terror attack in London, it has emerged.

The man, known only as L2 for legal reasons, was a member of the now banned radical group, al Muhajiroun, and was associated with friends of Lee Rigby's killer Michael Adebolajo and Jihadi John.

It is also claimed that he fought for Al Qaeda in the Islamic Maghreb against French forces in Mali and it was largely because of this that a move was made to 'prevent him from returning to the UK'.

The case emerged in a behind-closed-doors hearing by Home Office lawyers yesterday, which was so secret that even the man and his lawyers were banned from attending so that 'secret' evidence could be dissected.

The Nigerian man, known only as L2 for legal reasons, who was associated with friends of Lee Rigby's killer Michael Adebolajo and Jihadi John, had his UK citizenship revoked by Theresa May in late 2013 (file picture)

The man, who is said to have worked and lived in Tower Hamlets, east London, during his time in Britain, is fighting his revoked citizenship at the Special Immigration Appeals Commission in London.

His British nationality was removed by Home Secretary Theresa May in 2013 after he was deemed such a threat to national security that she personally signed off on an order removing his citizenship.

It came amid growing fears of extremists carrying out Paris-style massacre attacks in Europe.

According to the Bureau of Investigative Journalism, which is covering the case, an unnamed secret services agent – known as 'EZ' – told the hearing that L2 had once been 'engaged in terror activity'.

He said that in 2007, L2 had been in Turkey where he took part in 'terror-related activity' with Ali Adorus, a close associate of Mohammed Emwazi – otherwise known as ISIS frontman Jihadi John.

Adorus, now in an Ethiopian prison for terror related offences, was questioned alongside the ISIS executioner in 2009 when they travelled to Tanzania together for a 'safari', the hearing was told.

After returning to the UK, L2 spent a 'chunk of time' in a British prison between 2007 and 2011 for possessing a handgun. It was during this time he was said to have met Ibrahim Hassan, a known extremist who was friends with Lee Rigby's killer Michael Adebolajo.

Hassan was arrested two days after the 2013 Woolwich murder and later jailed for three years for encouraging terrorism.

The Nigerian man, known only as L2 for legal reasons, is said to have been directly associated with both Ibrahim Hassan (left) and Shah Jalal Hussein (right), who have both been jailed in Britain for terror offences

Following his release from prison, L2 is understood to have attended a string of meetings and demonstrations organised by al Muhajiroun - a now banned Salafi jihadi terrorist organisation.

Victoria Parsons, of the Bureau of Investigative Journalism, reported how he also worked at Master Printers – a printing shop in east London which was raided by police in 2011 over suspicions of links to al Muhajiroun - alongside Shah Jalal Hussein, now jailed for disseminating terrorist propaganda.

Their association was 'not just through their employment', agent EZ told yesterday's hearing.

The court heard how L2 and Hussein also knew each other because they were both founding members of proscribed terrorist organisation Minbar Ansar Deen.

The security services witness said L2 was also a close associate of al Muhajiroun member Afsor Ali, who was jailed for owning a bomb making guide and al Qaeda propaganda in August 2014.

The man's British nationality was removed by Home Secretary Theresa May in 2013 after he was deemed such a threat to national security that she personally signed off on an order removing his UK citizenship

In cross-examination, Hugh Southey QC, barrister for L2, said his client denied being a member of either al Muhajiroun or Minbar Ansar Deen, merely that he was acquainted with members.

Southey added that Minbar Ansar Deen was 'essentially just a website' which L2 strongly denies ever visiting.

However, the security services agent said their assessment was that he was a member, but that he could only give their evidence for that in a closed hearing.

The agent also outlined the circumstances leading up to Theresa May's decision in November 2013.

He told the court that L2 flew to Morocco with his wife in 2012 before travelling overland to Nigeria - passing through Mali, where he was assessed to have fought with Al Qaeda against French and Malian troops during the civil war.

Mr Southey said L2 denies this and instead claims L2 and his wife went to Nigeria because she was pregnant and it was cheaper for them to go to a maternity hospital there than to return to the UK.

But the intelligence agent suggested that account 'lacks credibility… it's a very very long journey through desert and war torn country' for a pregnant woman to make, he said.

Despite being known to the police for five years – and travelling to the US for 'tourist purposes' in that time – it wasn't until L2 lost his passport in Nigeria and applied for a new one so he could return to the UK that the Home Secretary acted.

L2, who is currently in Nigeria with his family, is now trying to challenge the order. However, his case at the Special Immigration Appeals Commission was almost halted this week when he wrote to the court saying he was 'boycotting the trial'.

'You can do as you wish with me and grant me no respite', he wrote, according to Jonathan Glasson QC, Home Office barrister, who read aloud from the letter in court.