THE London Bridge terrorist was banned from entering London but had a one-day exemption to attend an ex-convict event, it emerged last night.

Usman Khan, 28, from Staffordshire, was released from prison in December last year on condition he obey 20 strict conditions - which included not visiting the capital.

10 London Bridge attacker Usman Khan, 28, was convicted in 2012 for terrorism offences Credit: PA:Press Association

10 Haunting images show a Learning Together conference underway at Fishmongers' Hall before the violence erupted

10 Armed cops surround the terrorist on London Bridge

How the London Bridge terror attack unfolded

But the killer "hoodwinked" authorities by travelling to the prisoner rehabilitation conference at Fishmongers' Hall where he launched his horror rampage on Friday.

One academic who was there told the Mail On Sunday that Khan "suddenly just flipped".

Khan fatally stabbed Jack Merritt, a 25-year-old course coordinator, and a woman, before heroic members of the public wrested him to the ground and armed cops shot him dead.

'RUSSIAN ROULETTE'

The attack has prompted questions on why Khan, a convicted terrorist, had been released before the end of his original sentence.

Khan was jailed in 2012 for his involvement in plans to blow up the London Stock exchange, then then Mayor Boris Johnson's homes and the US embassy.

But when the Court of Appeal passed an extended sentence on Khan, he was given a 16-year custodial term and a 5-year extended licence.

Laws around extended sentences repeatedly change.

But at the time of his sentencing, prisoners serving extended sentences were released automatically halfway through their custodial term - which in this case was after eight years.

10 Jack Merritt, pictured with his girlfriend Leanne, was tragically killed in the terror attack unleashed by Usman Khan at London Bridge

DAY OF THE ATTACK

Under the terms of his release, Khan was required to wear a tag, have his movements monitored and attend deradicalisation sessions.

The Sun on Sunday can also reveal Khan was given “special permission” to attend the Cambridge University-run event.

The callous killer attended the morning session before returning after lunch to launch his rampage armed with two knives and a fake explosive vest.

Yesterday haunting pictures emerged of delegates inside the hall an hour before the carnage. Khan was said to be in the room at the time.

He is the first freed terrorist to launch an attack in this country.

Chris Phillips, a former head of the UK National Counter Terrorism Security Office, said on Saturday: “We are playing Russian roulette with people’s lives by letting convicted, known, radicalised jihadi criminals walk about our streets.

“The criminal justice system needs to look at itself.”

10 Haunting pictures have emerged of the Learning Together conference taking place at Fishmongers' Hall before the tragedy unfolded Credit: Learning Together/Twitter

10 Khan can be seen lying dead on London Bridge after being chased by brave heroes Credit: Cliff Hide for The Times

'I AIN'T NO TERRORIST'

Khan had shown signs of radicalisation prior to his 2012 arrest.

In chilling footage from 2008 he told BBC reporters: "I ain't no terrorist" after anti-terror cops raided his home.

A former classmate has also told how he saw him preaching with ISIS flags on the streets after the "lonely" teenager had finished Haywood High School in Burslem, Stoke.

It also emerged that Khan was a student of hate preacher Anjem Choudary before he was locked up for his bomb plot.

In 2012, he penned a letter from his jail cell for a deradicalisation course to become a "good British citizen."

In the letter, obtained by ITV News, Khan said he would be "grateful" of a course in which he could "properly learn Islam" so that he could prove he is a "good citizen of Britain."

Tonight ISIS announced it was responsible for the attack, but British security sources shed doubt on the claims.

Prime Minister Boris Johnson has claimed that scrapping early release from prison would have stopped him.

But Khan was released under a sentencing regime that no longer exists, and the changes Johnson has proposed to automatic release would not have applied to him.

The Ministry of Justice has now promised that "the licence conditions of every terrorist offender" would be reviewed going forward to ensure conditions "are as tough as they need to be".

A spokesman said on Saturday they were also "stepping up our already frequent meetings with these offenders".

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In a moving tribute, victim Jack Merritt's father David urged for moderation in the wake of his son's death.

He tweeted: "My son, Jack, who was killed in this attack, would not wish his death to be used as the pretext for more draconian sentences or for detaining people unnecessarily.

"R.I.P. Jack: you were a beautiful spirit who always took the side of the underdog."

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10 Footage from 2008 reveals Khan telling reporters he 'ain't no terrorist'

10 Emergency services can be seen giving a person CPR at London Bridge