Investigation launched into how he was able to move around freely

Counter terrorist forces think he had a fake passport and visited London

The mastermind behind the Paris terror attacks is believed to have visited the UK using a forged passport to seek logistical support from extremists in Britain weeks before carrying out the atrocity which killed 130 people.

It is understood Abdelhamid Abaaoud, 28, met fanatics in Britain last summer and travelled to London as part of his preparations for the horrific actions in the French capital.

The terrorist was killed in a police raid days after the Paris tragedy and is thought to have only been in the UK for a short time.

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Counter terrorism forces believe Abdelhamid Abaaoud, 28, pictured, entered the UK with a fake passport

The terror mastermind planned the Paris attacks in November which killed 130 people

Pictured: Emergency services tending to the wounded at the Bataclan Theatre, where 89 people were killed

Counter-terrorism agencies say they are convinced Abaaoud slipped into the country undetected and are investigating whether he arrived via Kent.

The current theory is he used a false passport to leave no trace of his arrival or departure through UK immigration services.

It has led to a major investigation in Europe and the US to determine how he was able to move freely despite his status as a wanted man.

French police later carried out a raid in Saint-Denis, Paris, where Abaaoud was killed

Pictured: Hundreds of people in Paris pay tribute at a memorial to those killed in the attacks

As previously reported, Abaaoud had pictures of reported 'targets' in Birmingham on his phone, raising fears he was plotting similar attacks in the UK.

He and Paris suicide bomber Brahim Abdeslam also made phone calls to numbers belonging to Moroccan nations living in Birmingham.

PARIS MASTERMIND WAS BEHIND OTHER EUROPEAN ATTACKS Once a student at one of Brussels' most prestigious high schools, Saint-Pierre d'Uccle, Abdelhamid Abaaoud morphed into Belgium's most notorious jihadi, a zealot so devoted to the holy war that he recruited his 13-year-old brother to join him in Syria. The child of Moroccan immigrants who grew up in the Belgian capital's scruffy Molenbeek-Saint-Jean neighbourhood, the fugitive in his late 20s was today identified by French authorities as the mastermind behind the Paris attacks. Abaaoud is believed to have links to earlier terror attacks that were thwarted: one against a Paris-bound high-speed train that was foiled by three young Americans in August, and the other against a church in the French capital's suburbs. 'All my life, I have seen the blood of Muslims flow,' Abaaoud said in a video made public in 2014. 'I pray that Allah will break the backs of those who oppose him, his soldiers and his admirers, and that he will exterminate them.' Belgian authorities suspect him of also helping organize and finance a terror cell in the eastern city of Verviers that was broken up in an armed police raid on January 15, in which two of his presumed accomplices were killed. The following month, Abaaoud was quoted by the ISIS' English magazine, Dabiq, as saying that he had secretly returned to Belgium to lead the terror cell and then escaped back to Syria despite having his picture published. He said: 'I was even stopped by an officer who contemplated me so as to compare me to the picture, but he let me go, as he did not see the resemblance'. Advertisement

A counter terrorism source told The Sun: 'We believe those calls were made to discuss some aspect of logistics and finances with regards to the Paris attacks. We also think money and false or doctored documents swapped hands between Abaaoud and Brahim and their associates in Birmingham.

'Forensic evidence suggests some of the forged documents found on Paris attackers were personally handed over to Brahim and Abaaoud during visits to the UK.'

A Mail on Sunday investigation discovered the notorious jihadi, who had been linked to four foiled plots this year alone, was in regular contact with a 'network of associates' in the Midlands in the weeks before the Paris strikes, insiders believe.

Born in Belgium, Abaaoud left his home in 2013 for Syria where he trained alongside fellow extremists.

He returned to Belgium to organise a plot to kill police officers, but managed to escape when it was foiled last January.

A manhunt was launched but he evaded authorities and returned to Syria, and claimed to have made it past a Belgian border officer after he failed to recognise him from his mugshot.

He was later sentenced to 20 years in prison in his absence by a Belgian court.

According to the De Standaard newspaper, Abaaoud is also mentioned in files relating to Brahim Abdeslam for alleged crimes carried out in Brussels in 2010 and 2011.

Abaaoud even featured in an online ISIS terror magazine Dabiq featuring his life as a Jihadi.

According to the interview, he traveled to Syria 'to terrorise the crusaders waging war against the Muslims'.

He said: 'Belgium is a member of the crusader coalition attacking the Muslims of Iraq and Sham (Syria).

Abaaoud claimed that in the past he returned to Belgium to set up a safe house to plan further raids across Europe.

He said his plot failed: 'The kuffar raided the pace with more than 150 soldiers from both French and Belgian special forces units.' He said both of his men were killed in the shootout.

Floral tributes were also left at Place de la Republique in Paris honouring the victims' memories

He claimed it was after this, he returned to Syria due to the attentions of European security agencies.

French police have said Abaaoud planned the attack from his base in Syria with help in Belgium and France.