A MAN in his 20s is fighting for life after being stabbed 'after an argument' in Costa Coffee this morning.

A suspect has since been arrested after the brawl in Arnos Grove, North London.

It comes as knife violence around Lawless London continues to rise.

A witness today told the Sun Online how they saw the suspect in a suit and cap before he was taken away by police.

He said: “He was just sat on the floor like nothing had happened.

“He was just very calm, it was eerie.”

The witness added he spotted the knife, which had a blade of about 4inches, on the ground after the attack.

Local resident Burak Demieci, 30, said that a man came out of the coffee shop and began to run down a side street.

He said: "It was really weird - the man that did the stabbing was so calm.

"He just jogged halfway down the road and gave up and walked away slowly.

"A black man in his early twenties chased him down and somehow convinced the man to hand himself in.

"I don't know who that man was, but he was brave to approach the suspect.

Met Police are now investigating after the attack in the cafe on Bowes Road.

A spokesperson said: "Officers attended alongside the LAS and London’s air ambulance and found a man suffering from stab injuries. He was taken to hospital in a life threatening condition.

"One man was arrested at the scene and taken to a nearby police station where he remains in custody. Enquiries continue."

London Ambulance crews confirmed they had been called to Arnos Grove about 11.30am.

They said: “We treated a man at the scene and took him to a major trauma centre as a priority by road."

A Costa Coffee spokesperson said: "“We are aware of the incident and will continue to support the local police authorities in their on-going investigations."