The court heard Kevin Davies, 39, of Blaenavon, used "excessive force" when trying to break up an argument.
The moment a doorman broke the jaw of a passing Ed Sheeran fan after a concert in Cardiff was caught on CCTV.Kevin Davies, 39, of Blaenavon, was on the door of a bar on St Mary Street when he pushed and punched Michael Barraclough, who was on his way home from the concert at the Principality Stadium.
Davies was convicted of causing grievous bodily harm and will lose his security licence as a result of his conviction.
He was handed a 12-month suspended sentence and ordered to pay Mr Barraclough £800 compensation.
Mr Barraclough suffered a broken cheekbone, eye socket and jaw in the "brutal unprovoked attack" which was filmed on CCTV.
Cardiff Crown Court court heard Davies was working as a doorman at For Your Eyes Only in Cardiff when Mr Barraclough and his girlfriend passed on their way home from the show.
Nuhu Gobir, prosecuting, said CCTV showed Davies "delivering a blindside punch to the right side of his face."
He said: "That punch immediately and forcefully sends the complainant to the floor.
"He grabbed the complainant’s T-shirt close to his collar with both fists and swung him around and he delivered another forceful punch, this time to the left side of the complainant’s face.
Mr Gobir asked Mr Barraclough: "Had you done anything to provoke the doorman?”
He told the jury: "I wouldn’t know him from Adam. I think he went steaming in and knocked me out cold.
"In my eyes it was an unprovoked attack.”
He told the police he hit Mr Barraclough in self-defence as part of a “pre-emptive strike”.
Davies claimed he stepped in to protect girlfriend Karina Tufft after claiming the victim was being “aggressive” to her.
Jurors were told the couple had argued walking down St Mary Street while looking for food after going out drinking in Cardiff city centre following the gig.
The court heard Davies initially pushed Mr Barraclough to the floor "with excessive force" before the two men came together and he punched him.
Miss Tufft told jurors her then boyfriend was “shouting in her face” before he was struck by Davies.
Footage of the assault was recorded from a camera at the neighbouring Taco Bell restaurant.
Sol Hartley, defending, said: "He will lose a job which he enjoyed and a job that provided a future for him and can't earn as he did before."
Judge Recorder Sean Bradley said: "You punched him directly in the face with a very significant and clearly excessive degree of force.
"It's clear to me you seriously misjudged this situation. You rushed in to defend Miss Tufft when there was no need to.
"You're a big man and even if you had intended to protect Miss Tufft you clearly used excessive force."
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