A Nigerian closely connected to a notorious group of British Islamists has been stripped of his UK citizenship amid fears he would return to London to execute a Paris-style massacre, a court has heard.

The man, known only as L2 for legal reasons, was deemed such a national security threat by Home Secretary Theresa May that she personally signed an order removing his British nationality in 2013, it has emerged.

He was in Nigeria at the time, where he remains with family. He is now challenging Theresa May’s decision at the Special Immigration Appeals Commission in London.

At the hearing on Tuesday, an unnamed secret services agent referred to as ‘EZ’, told the court that during his time in Britain, L2 had been a member of the now banned group of radicals, al Muhajiroun.

Agent EZ said that through his other experiences L2, who is understood to maintain Nigerian citizenship, was also directly associated with close friends of Lee Rigby’s killer, Michael Adebolajo, and Mohammed Emwazi, or “Jihadi John”.

Paris attacks suspect caught

He also said L2 had fought for Al Qaeda in the Islamic Maghreb (AQIM) against French forces in Mali and it was largely as a result of this assessment that a move was made to “prevent L2 returning to the UK”.

“We were trying to prevent L2 bringing back the expertise he would have learnt with AQIM and so a deprivation order was the best course to take,” he told Siac.

Recent events such as last year’s Paris attacks suggest extremists are returning to conduct their jihad in Europe, he said, including “instances where individuals from the UK have travelled overseas and returned to conduct attacks”.

UK terror plots that were foiled by security services Show all 14 1 /14 UK terror plots that were foiled by security services UK terror plots that were foiled by security services Oxford Street terror plot Lewis Ludlow was jailed for life in March 2019 for planning a 'spectacular multi-victim attack' on Oxford Street in London. He pleaded guilty at the Old Bailey last year to plotting an attack in the UK and funding Isis abroad EPA UK terror plots that were foiled by security services Rosie Cooper MP plot Jack Renshaw admitted plotting to kill his local Labour MP with a machete in June 2018. Renshaw bought a 19in machete intending to use it to kill Rosie Cooper, MP for West Lancashire. His plan was foiled by whistleblower Robbie Mullen, who heard of the plot in a meeting of alleged and convicted National Action members in the Friar Penketh pub in Warrington Hope Not Hate UK terror plots that were foiled by security services 'Poppy terror plot' Nadir Ali Sayed, his cousin Yousaf Shah Syed, and Haseeb Hamayoon, were charged with terrorism offences over an alleged plot to behead a member of public. The trio were arrested in London and High Wycombe, Buckinghamshire on 6 November - three days before Remembrance Sunday in 2014 PA UK terror plots that were foiled by security services National Action arrests Following the arrest of six men in 2018 on suspicion that they were members of the banned far-right terror group National Action, two were jailed. Christopher Lythgoe was found to be leader of the banned group and jailed for eight years, while Matthew Hankinson was jailed for six years. While it was found that Lythgoe did not encourage Jack Renshaw's plot to kill a Labour MP, the judge noted that he "did nothing to stop or discourage" the attack PA UK terror plots that were foiled by security services Shane Fletcher A self-described 'loner', Fletcher planned to kill members of the public at a football match in his home town of Workington. He had been referred to the government's Prevent programme nine moths prior to his arrest after stating that he dreamed about "shooting up a mosque" PA UK terror plots that were foiled by security services Heathrow airport arrests A 19-year-old from Coventry man was arrested at London's Heathrow airport on suspicion of preparing for acts of terrorism in November 2014 UK terror plots that were foiled by security services Extradition of Abu Hamza Radical muslim cleric Abu Hamza was extradited to the US in 2014 after having been jailed in the UK for 7 years for 11 offences under the Terrorism Act Getty UK terror plots that were foiled by security services South East Counter Terrorism Unit arrests Six people were arrested on suspicion of terrorism offences after a series of dawn raids in the south of England in October 2014. Three men and three women were detained separately in two properties in Portsmouth, one in Farnborough and one in Greenwich following an operation by the South East Counter Terrorism Unit. Counter-terror officers said they had disrupted what was believed to be the early stages of what could have turned into a “significant plot” PA UK terror plots that were foiled by security services October 2014 arrests Three men were arrested in central London on 13 October as part of an investigation into Islamist-related terrorism. The arrests come nearly a week after five men were arrested in dawn raids that Whitehall officials said “may have foiled the early stages” of a plan to attack the UK Peter Macdiarmid/Getty UK terror plots that were foiled by security services Anjem Choudary arrest Anjem Choudary, the radical activist and co-founder of the banned al-Muhajiroun group, was arrested in September 2014 as efforts intensify to disrupt the ideological backers of young British Muslims travelling to fight in foreign conflicts. Mr Choudary was among nine men held on suspicion of supporting a banned terrorist group and encouraging terrorism. The arrests came shortly after Mr Choudary fired off a series of angry tweets after David Cameron called on MPs to back air strikes against Islamic State militants in Syria Oli Scarff/Getty UK terror plots that were foiled by security services North West Counter Terrorism Unit funds seizing Police seize £250,000 of cash intended to fund Isis at Manchester Airport and north-west ports. Using powers under the Terrorism Act, the money was confiscated by officers from the North West Counter Terrorism Unit in Ocotber 2014 Getty UK terror plots that were foiled by security services Tarik Hassane arrest A medical student who was offered a place at a London university has been named among four men who are being questioned by counter-terror police after a series of raids across the capital. Tarik Hassane, 21, is believed to have been Tasered when he was arrested on suspicion of being involved in a "significant" Islamist terror plot on 7 October 2015 UK terror plots that were foiled by security services Abu Qatada removed from UK Radical preacher Abu Qatada will not be returning to the UK after being cleared of terror charges in Jordan in 2013 Reuters UK terror plots that were foiled by security services Haider Ahmed knife plot Teenage Isis supporter Haider Ahmed purchased a 15ins hunting knife and threatened to launch a stabbing attack on the Tube. Prosecutors said he may alternatively have been planning to rob someone with the weapon to fund his travel to fight for Isis in Syria He was jailed for preparing an act of terrorism in June 2019 Counter Terrorism Policing South East

The Bureau of Investigative Journalism is covering the case for The Independent as part of a long running investigation into the Government’s counter terrorism powers and the use of secret evidence in courts such as Siac.

The second day of L2’s appeal today was held in closed session for secret evidence to be presented to the judges by the Home Office lawyers. Neither L2 nor his lawyers are allowed to hear it.

During the open session on Tuesday, the intelligence agent described various links between L2 and known extremists.

He said that in 2007, L2 had been in Turkey where he “engaged in terror related activity” with Ali Adorus, a close associate of Emwazi. Adorus, now in an Ethiopian prison for terror related offences, was questioned alongside the IS executioner in 2009 when they travelled to Tanzania together for a “safari”.

After returning from Turkey, L2 spent “a chunk of time” in a UK prison, sometime between 2007 and 2011 for possessing a handgun, the court heard.

Allegedly, it was while he was in jail that he met Ibrahim Hassan, a known extremist who was friends with Lee Rigby killer Michael Adebolajo. Hassan was arrested two days after the 2013 Woolwich murder and later jailed for three years for encouraging terrorism.

Siac heard that after L2 was released from prison he attended al Muhajiroun meetings and demonstrations.

The agent also said L2 worked at Master Printers in Tower Hamlets, east London – a printing shop raided by police in 2011 over suspicions of links to al Muhajiroun.

He said that at Master Printers, L2 worked alongside Shah Jalal Hussein, who was tried in 2014 for disseminating terrorist propaganda and jailed for three years.

Their association was “not just through their employment”, the agent said.

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

The court heard how L2 tried to register a domain name for the organisation on the internet.

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.

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

Home Secretary Theresa May personally signed an order removing the man's British nationality (EPA)

The agent also told the court of the circumstances leading up to Theresa May’s decision in November 2013.

He said L2 flew to Morocco with his wife in 2012, and then travelled 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.

Southey said L2 denies this. He said L2 says he and his wife went to Nigeria because she was pregnant and it was cheaper for them to go overland to a maternity hospital in Nigeria 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.

This week’s case in Siac was almost derailed at the start of the hearing when L2 wrote to the court saying he wanted nothing to do with his appeal and 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.