ASK Gary Skjoldmose-Porter about pirates and he won't make the same mistake as the ladies of the Parkham Women's Institute.

The WI members infamously dressed up in eye patches and stripey jumpers when told they were going to hear a talk about the high seas. Skjoldmose-Porter, who advised on and acted in the new Danish thriller A Hijacking, knows from personal experience the true colours of pirates.

"They're definitely not Jack Sparrow, I can tell you that," says the corporate security manager for the Clipper Group shipping company, speaking from his office in Copenhagen.

"These are people from Somalia, they are desperate young individuals who have nothing. If someone offers them the chance to earn $5000 or $10,000 to get into a hostage situation when their daily wage is maybe one or two dollars, then they are going to jump at it."

A Hijacking, directed by Tobias Lindholm, is set on the cargo ship MV Rozen. While heading through the Indian Ocean, its crew are taken hostage. As millions of dollars are demanded in ransom, the shipping company goes into emergency response mode, calling in a professional negotiator to lead the talks.

Skjoldmose-Porter, below, has been in that kind of room. In 2008, one of his company's vessels was hijacked, with the stand-off lasting for 71 days. Everyone was released, with Skjoldmose-Porter helping to organise the ransom drop.

The experience gave him an insight that he has since passed on to other companies, law enforcement agencies – and now the film industry.

Lindholm had asked the ex-British military man to brief the cast and crew. A session that was supposed to last 20 minutes went on for three hours, at the end of which Skjoldmose-Porter was asked to play the security adviser in the film.

One of the character's key pieces of advice is that the person who deals directly with the pirates must not be personally involved. It is a rule promptly broken in the drama by a boss who quickly finds himself out of his depth.

In 2008, Skjoldmose-Porter was, like many others, learning about piracy from a standing start.

"We can deal with a collision, a grounding, a fire or anything else because you get trained in that, but a piracy situation, nobody deals with that really. Well, they didn't in 2008, that was sort of the beginning of it. A lot of people know what they are doing now, but at that time there was only a few people dealing with the subject."

Some of the most tense scenes in the film take place in the shipping company's emergency room. It must be hard, I suggest, to remain detached in such a fraught situation.

"It is, because they are men you know. You work with these people. Ships captains don't just come and go. You know their families, their kids, you just think, ah come on, this is a normal family man with the rest of his crew going about their lawful business, going to work the same as me and you do, and getting a gun put into his face and being held." It's an "obscene" situation, but emotions have to be held in check. "If you start getting angry then you lose everything."

David Cameron, the Prime Minister, this week hosted an international summit in London aimed at helping Somalia shake off its "failed state" tag. Though the number of hijackings has gone down dramatically, largely due to the actions of a new government in Somalia and the readiness of shipping companies and countries to protect their vessels, the threat has not been eradicated.

Skjoldmose-Porter, for one, is not complacent. "The amount of piracy incidents in the high-risk area has decreased a great deal over this last six months but, and this is what people keep forgetting, the pirates still have the capability to come straight back."

As he says, it only takes a skiff, a gang of desperate young men, an outboard motor and fuel, and a piracy gang can be back in business. His firm takes no chances: besides having ex-British marines on board, the ships are armed.

One downside to hijackings becoming more difficult to pull off is that they can be more brutal. "Maybe it's because the pirates are getting more desperate," says Skjoldmose-Porter. "I don't know. But it's not good, you don't want to be caught now that's for sure. In 2008, in comparison to now, we got away lightly."

Hijackers these days also have the added advantage of satellite phones and internet, through which they can put more pressure on families and firms.

Though he had never acted before A Hijacking, Skjoldmose-Porter is used to explaining what he does in lectures given all over the world. "Going in front of a camera is not much different from just talking to normal people," he reckons. And, he adds, "They were nice to me."

Originally from Ipswich, he went on holiday to Denmark and met the woman who was to become his wife. Three children later, he loves it there. His wife has seen the film, which has been a huge hit in Denmark. And her review? "She said 'Oh well done, pat on the back. Now get back to work and earn a living'."

Glasgow Film Theatre, Cameo, Edinburgh, and Aberdeen Belmont, from tomorrow; Filmhouse, Edinburgh, May 17-23; DCA, Dundee, May 31.