But Herinckx is no battle-hardened prize-fighter. He's one of a number of white collar London office workers who have spent the last few months training to box and tonight is fight night.

"It's like every moment was frozen in time. It was like fight or flight," Herinckx told Reuters after his bout.

As he spoke, the packed crowd gathered at an arena in southeast London were already erupting in a roar for the next city professional swaggering towards the ring, swathed in laser lights, smoke-machine effects and the pumping beat of music.

Herinckx and the other 37 boxers strutting their stuff on Friday night have spent the last three months on a gruelling three days a week training routine run by Chrissy Morton, founder of Bad Boy Promotions.

"As soon as one of the guys on signs up, they all have to," Morton told Reuters. "It passes from one to the other. If they don't do it - well...it's a rite of passage."

"We train the white-collars like professional boxers; they go from being a normal person in the office to someone who can go out there and fight in a ring."

Morton doesn't charge for the training period, relying on the boxers to raise money through ticket sales to their friends and colleagues. Many of them sold as many as 50 tickets.

Workers in London's financial district known as the "City" are naturally competitive and having achieved financial success at a relatively young age, may see the chance to fight it out in a gladiatorial tournament as a natural progression.

Just before his big fight, Ed Vinales, news editor at DealReporter.com, a Financial Times company, said it had been a steep learning curve which he enjoyed because boxing training makes you lose weight fast.

"Once you see a few bloody noses in the sparring sessions you quickly learn to move your feet and head," Vinales added.

Morton says the physical change she sees in her boxers as they prepare for their three, 90-second rounds of heavy hitting is staggering.

"They come in and they've all got beer bellies, she said. "Too many late nights taking clients out; you find that you don't do that anymore."

The training takes place at TRAD TKO Boxing Gym deep in London's East End.

A week before the big fight, its three rings were full of 20- and 30-somethings working on their ring craft - ducking, swerving and jabbing rhythmically into the air.

Nearby, sweat-ridden trainees skip, do press-ups, squat-thrusts, sprints, while others lay into heavy punching bags.

Despite the violence, serious injuries are minimal at white-collar events.

"The worse they get is a bloody nose or an attack of nerves," Morton told Reuters.

"They're well-protected and I've got an excellent referee."

As well as the mandatory gum shields, white-collar fighters wear headguards and 16 oz gloves (compared to the 8-10 oz professional glove). Women boxers wear chest protectors.

Promoter Morton has been trying to even up the male-female boxing ratio, but it hasn't been easy.

"Women do come in, and then they do fall out," Morton said during a training session at the boxing gym.

"Some just come to get the free training. Once they get hit in the face, they change their minds."

The female bouts didn't disappoint the Troxy crowd; former Team GB high jumper Ayamba Akim's victorious bout against veterinarian Kimberley Anley was one of the standout fights of the night.

But it was news editor Vinales who achieved the only technical knockout of the night.

"I think I'm going to do it again in about six months," Vinales told Reuters moments after his victory. "Hopefully next time it will go the full three rounds."

Another winner, a commodities trader named Guy Burgoyne whose rapid-fire jabbing drew gasps from the crowd, described how boxing was the ultimate antidote to a computer-flanked existence, allowing "West London" boys like him to do something gritty and real.

"Let's face it, every man wants to be the centre of attention," Burgoyne said with a smile.

Promoter Morton's next white-collar event will be staged on June 29, 2012; training begins on April 11. Prospective weekend warriors can sign up at www.badboypromotions.co.uk.

(Editing by Paul Casciato)

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