Inside the sinister world of hired guns, the targets billionaires pay them to 'neutralize' ... and the chilling details Hollywood gets wrong

A real-life mercenary has lifted the lid on the outrageous excesses and sordid tactics of a modern 'gun for hire' - and revealed how he ended up languishing for 18 months in a Serbian jail, fighting for his freedom.

A former Navy SEAL, Daniel Corbett concedes that his career of choice is morally ambiguous - even if his targets are the 'bad guys': terrorists, bomb makers, rebel commanders, and other enemies of the US.

But, after retiring from the military in 2012, the money on offer proved too tempting to resist.

His first contract - guarding cargo ships against Somali pirates in the Indian Ocean - came with a pay packet of $20,000 per month, and in just three months, he'd made more than he earned in a year in the navy. That was enough to get him hooked.

Working for an 'elite outfit of private contractors', what he does is, he says, legal, sanctioned by the US government, unofficially, and takes him all over the world - from Abu Dhabi to Washington, DC , Cairo to San Diego.

And it involves more than just 'neutralizing' (mercenaries prefer this term to 'killing' for obvious reasons) enemy targets.

'Some jobs require finding kids who have been kidnapped by their father and returning them to their mom,' he says. 'Some jobs involve confronting card-carrying KKK members over debts they owe. Some mean recovering hostages from terrorists, or liberating children from the grip of warlords.'

Wherever he goes, though, money is king - and his uber-rich paymasters make sure he travels in style.

In his new book, American Mercenary : The Riveting, High-Risk World of an Elite SEAL Team Operator Turned Hired Gun, Corbett - whose nickname is Dirty - describes a typical job, with an almost fatal outcome.

After a call from his handler, asking him to meet in Abu Dhabi, Corbett flies - Etihad business class - direct to the UAE capital and checks into a luxurious suite at the Four Seasons.

His handler, Malachi, is waiting for him in the lounge and, together, the pair head to the exclusive steak house Nusr-Et, to meet the client.

He 'must remain anonymous, so let's just call him Al,' writes Corbett. 'He's a repeat client and by now we're all friends - or at least very friendly.'

What he does reveal is that 'Al' is a very wealthy Emirati, with a very particular request.

'A hostess leads us to our table - the best in the house, a private seat overlooking a blue inlet leading to the Persian Gulf.'

Technically, the UAE is dry, but since they are westerners staying in a luxury hotel, and are being entertained by such a high-ranking host, the wine flows.

They down a $1,200 bottle of French cabernet - then another - before they are presented with a wooden cutting board overflowing with steak and lamb.

'At one point Nusret himself, aka Salt Bae , stops by to ask if we're satisfied.

'We are. He sends another small course of exceptional filets. I can't resist, forcing down a few more bites.'

At the end of all this wining and dining, Corbett is finally briefed on his target: a lead member of a group that finances Houthi militants in Yemen , but who is at that time living in the relative safety of Belgrade, Serbia.

'If the job were in France or Germany or the UK,' says Corbett, 'we would reject it outright. But Serbia has a weak and corrupt law enforcement system, making it easier to get out of the place in a pinch.

'Our task - really my task, since this will be a solo mission - is to spend a couple of months gathering incriminating intel on the target. Anything Al can use as leverage "to compel him" - Al's phrase - to stop financing the Houthis.'

Corbett retires to his suite, to research the target 'Peter' - checking his LinkedIn, his social media, etc. He finds out that he's the owner of a PR business with nine employees, and in his spare time enjoys museums, fine dining, fashion shows, and nightclubs.

Peter is also believed to frequent prostitutes, and if Corbett can get proof, it could be enough to cut off this source of the Houthis' funding.

'The job officially begins in five days,' he writes, 'meaning we have time to kill. It's not a good idea to fly directly from a client's location to the place you'll be working, so the next afternoon, Malachi and I fly to Cairo.

'We're not there on business, we're tourists. We hire a guide, visit the Pyramids, take stupid tourist pictures, and have a ton of fun. We even ride camels, and the camels saunter past the Sphinx. It's the first time I've done anything remotely normal in any Middle Eastern country. It feels good.'

This, says Corbett, is standard procedure for someone in his line of work - and is in stark contrast to the Hollywood portrayal.

'You can't pull a Jason Bourne with multiple passports and identities in this era of biometrics,' he says. 'You enter countries as yourself, with your legitimate passport.

'Yes, someone from that country might follow you around to see what you're up to. So for jobs like that, you do touristy, boring things for a few days. Hang out at bars and clubs, see the sights, chat up people who have nothing to do with the job. Become uninteresting, and your watchers move on. Then you can do whatever it is you're there to do.'

He adds that he always travels with cash not credit cards - but never more than $10,000. 'If you need more, you get a trusted source to make a run. Only euros or American dollars, every other currency is trash.'

Sometimes he's called to conceal his identity, and Hollywood's love of a good disguise is bang on the money, he says - from wigs, to make-up, and larger shoes all helping them cover their tracks. He's even been known to stuff outsize clothes with newspaper to make himself look bigger.

'What about DNA? Hollywood loves working with this one, and filmmakers can get it right too,' writes Corbett.

To avoid leaving a trace of his presence, tactics can include wearing a shower cap, shaving, and putting Vaseline on his eyebrows and up his nose. But often a more effective ruse is what he calls 'DNA confusion'.

'Litter a scene with enough evidence, and pictures become blurry. Sometimes mercenaries will gather used cigarette butts and drinking glasses, even pubic hairs from the bottoms of urinals, and leave them here and there.'

As for weapons and gadgetry, the on-screen portrayal more often than not misses the mark.

'Often we see our protagonist open a suitcase with enough guns to arm a dozen men, GPS trackers, butterfly knives, lethal doses of poison, C-4, and so on.

'In the real world, you're responsible for getting what you need. You need a high-end SLR camera? Go buy one. You need a GPS tracker? Make one. You need weapons? Find a way.'

Unfortunately for Corbett, weaponry proved to be his downfall. Within a month of landing in Belgrade, he was arrested at gunpoint and thrown in a Serbian jail. His charge: possession of an illegal handgun.

He claims never to have touched a gun in the country, and that Serbian cops planted his DNA on a weapon, hoping to charge him with plotting to kill the president, Aleksandar Vučić .

He spent the next 18 months fighting the charges, going through a drawn-out legal process, and when he was eventually released without charge, he could hardly believe it.

On the day the verdict was read out, he writes: 'I catch a few words here and there, but that's it. The translator asks for clarification on something. The judge nods in my direction and speaks quickly.

'The translator turns to me and says, "You can go, you can go."'

Corbett asks: 'I'm done? I'm free? Under what conditions? I need to know exactly what the judge said.'

After more discussion, the judge turns directly to him and says: 'You are innocent of all charges, Mr Corbett. The court is terribly sorry this has happened to you. On behalf of the Serbian government, I hope that your ordeal has not ruined your perception of Serbia. Our government will pay any and all legal fees, as well as restitution for missed wages and damages.'

They then add: 'You must immediately leave Serbia, as your visa has expired.'

Corbett stifles a laugh at what he calls 'this final absurdity'.

'But who am I to argue? I am free.'

The whole thing sounds almost too wild to be true. Indeed, while the book has been reviewed - and heavily redacted in places - by the Pentagon, it includes this disclaimer: 'The public release clearance of this publication by the Department of Defense does not imply Department of Defense endorsement or factual accuracy of the material.'

For his part, now based in San Diego, and despite his horrific experiences, Corbett says he has resisted the lure of a safe desk job. Instead, he continues to entertain phone calls and meetings with those who need 'unique solutions to unique problems.'

American Mercenary: The Riveting, High-Risk World of an Elite SEAL Team Operator Turned Hired Gun by Daniel Corbett is published by Center Street