"I trust them completely.": The true story that inspired the term Stockholm syndrome.

For six days inside a Stockholm bank, three women and one man were held captive by two armed robbers.

They were holed up inside a cramped bank vault, while the ordeal was broadcast live to Sweden and the world.

It started on the morning of August 23, 1973. The staff of Sveriges Kreditbanken, one of the country’s biggest banks, went about their days as normal: Piling papers, serving customers and chatting.

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Then 32-year-old Jan-Erik ‘Janne’ Olsson, carrying a folded jacket and a suitcase, entered the bank. The jacket concealed a loaded sub-machine gun and his case was full of ammunition, explosives and rope.

He pulled out his gun and fired it at the ceiling: “The party has just begun!” he shouted in English, disguising his voice with an American accent.

After wounding a policeman who had responded to a silent alarm, Olsson took four bank employees hostage. He – a safe-cracker who did not return to prison after a furlough from his three-year sentence for grand larceny – made his demands: He wanted more than $700,000 in Swedish and foreign currency, a getaway car and the release of his friend Clark Olofsson, who was serving time for armed robbery and acting as an accessory in the 1966 murder of a police officer.

Police obliged. Before long, Olofsson was released and delivered to Olsson to assist. Police also provided the ransom and a blue Ford Mustang for the getaway. The only thing police denied was Olsson’s demand to leave with his hostages.

Olsson, Olofsson and their four captives remained inside a bank vault for six days.

It would have been, one would imagine, a traumatic experience for the four bank employees involved.

But after six days - after they'd finally been released - the hostages told a very different story.

They were the reason the term Stockholm syndrome was coined.

When the youngest captive, 23-year-old Kristen Enmark shivered, Olsson draped his wool jacket over her shoulders. He soothed her when she had a bad dream. As a momento, he gave her a bullet from his gun.

Enmark spoke to Prime Minister Olof Palme over the phone and told him not to attempt to free them.

"I'm not one bit afraid of those two," she told him. "I trust them completely. Can't you just let us go with them?'

When Birgitta Lundblad could not get hold of her family by phone, Olsson told her to keep trying: "Don't give up," he said.

Elizabeth Oldgren suffered from claustrophobia in the cramped vault, so Olsson allowed her to walk outside of it attached to a nine-metre rope.

The hostages and the captors were on first name basis by day two. In fact, the three women and lone man - Sven Safstrom - began to fear the police more than they did the men who kept them captive, armed with powerful guns.

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Finally, after more than 130 hours, the police pumped teargas into the vault and Olafsson and Olsson surrended.

Police called for the hostages to come out first, but they refused.

"No, Jan and Clark go first - you'll gun them down if we do!" Enmark told them.

The six of them embraced in the doorway of the vault, and as police seized the gunmen, two of the women cried.

It was a response that perplexed authorities, psychiatrists and the captives themselves, who wondered if their reactions meant there was something wrong with them.

Even after the gunmen returned to prison, the hostages made visits to see them inside.