OUT of work and skint, Idris Price jumped at the chance to swallow a pill for ten consecutive days and be paid £250 for it.
It was part of a 1992 'guinea pig' trial of a new drug to treat angina, but many participants soon found they were suffering from a bizarre side effect - frequent and long-lasting erections.
The revelations stunned scientists and soon Merthyr Tydfil, South Wales, was home to a sexual revolution that saw the birth of Viagra.
This year marks the 25th anniversary of the drug's release, which has since helped millions of men with erectile dysfunction.
Its incredible story is told in a new documentary Keeping It Up: The Story of Viagra, on BBC Two tonight at 9pm.
It begins in the early 1990s, when pharmaceutical giant Pfizer trialled the drug - then known as UK92480 - which was believed to alleviate chest pain.
READ MORE FEATURES
At the same time, Wales was going through one of its toughest economic declines.
Due to a downturn in heavy industry, more than 352,000 blue collar workers were laid off and subsequently desperate to support their families.
Idris said: "In the 80s and 90s, it was very hard times - you had to try to get whatever money you could get.
"The factory that I worked in was a steel factory, very heavy equipment, you had to be very fit to work to do the job.
Most read in News TV
"I was there for about eight years and then they laid me off.
"If I was short of money I used to go down to this place called Simbec."
Simbec, a UK-based clinical research organisation that had a lab in Merthyr Tydfil, had hundreds of unemployed workers knocking on their doors to turn an easy quid.
Idris said: "I went down and said 'I've got a week off from work, is there any studies I can do?' and I was very surprised when they said yes, and that they had a course.
"I said 'what does it entail' and they said, 'You just take a tablet.'
"They called us guinea pigs back then because you were testing a drug that had never been tested before.
"The fear was if I was ill, seriously ill, that’s what frightened me."
In the 80s and 90s, it was very hard times - you had to try to get whatever money you could get
Idris Price
As part of the study, the local volunteers were asked to take a pill three times a day for ten consecutive days and would be paid £250 - the equivalent of over £450 today - to participate.
Idris said: "[The money] was very important, we had nothing in them days, nothing.
"Obviously you get extra food in with that money, or you get the coal fire going, instead of having two bags of coal, you'd have five bags of coal.
"We were told nothing about the drug. The doctor would say it was for angina... you will have side effects or you might not. [But] it was a doddle, it was easy money."
Not long after, the patients began reporting unexpected erections.
Lightbulb moment
According to the documentary, a lot of the men were reportedly nervous about revealing the unexpected side effect.
Dr Pete Ellis, Pfizer's former discovery and development lead, who took part in the trials, said: "Volunteers started coming forward and saying, 'It's a little embarrassing, but I've noticed I'm getting more erections than usual. And the erections are a lot harder than usual.
"They were all young men and I think it became a topic of conversation among them.
"Gradually more and more of them started reporting this erection side effect."
David Brown, a Viagra co-founder, was stunned by the results and soon launched an impotence study.
Brown added: "That’s when the lightbulb went on and we said, 'Hey we’ve got something here'."
Monkey testicle 'cure'
Attempts to treat impotence had been tested before. In the 1920s a Russian surgeon named Serge Abrahamovitch Voronoff trialled grafting monkey testicles onto humans.
The theory was part of the monkey testicle would boost levels of testosterone to give back potency and manly vigour.
At the time people were reportedly so interested in the trials that the public looked into buying an island just to keep the monkeys on.
Later in the 20th century the penis pump - which creates a vacuum around the penis, encouraging blood flow and causing an erection - was invented. However, this contraption also had mixed results.
Volunteers started coming forward and saying, 'It's a little embarrassing, but I've noticed I'm getting more erections than usual. And the erections are a lot harder than usual
Dr Pete Ellis, Pfizer's former discovery and development lead
Following the revelations at Simtec, Pfizer funded a wider impotence study.
Patients with erectile dysfunction were tested at Bristol's Southmead Hospital, before a further clinical trial in 1994 in Swansea.
David Price, trial leader and endocrinology consultant, recalled of the tests: "Pfizer said they had to be heterosexual men in a stable relationship.
"They were all regular guys, all married and ordinary blue collar Swansea men. The trial included showing the men erotic videos."
A device was attached to the men's penises to monitor the drug's impact - which came back positive.
Pfizer quickly realised they had a game-changing drug on their hands.
Idris recalled the trial being quite arduous: "You couldn't leave the building, you couldn’t go anywhere… and then in the evening we would relax.
"I was amazed when I found out. Viagra is a big thing now. I was part of that study and I'm glad it was found out in Merthyr Tydfil."
The little blue pill that 'saves marriages'
In 1998, Pfizer released its first batch of Viagra in New York - with orders surging through the roof.
With the 'life changing' drug exceeding its sale predictions, a group of experts teamed up to drive exponential growth of the product.
Marketing execs designed the "simple pill" in a calming blue colour, which had a diamond shape to show strength, while the name Viagra was selected to sound like vigour.
Pfizer's marketing team even managed to get a meeting with the Vatican to discuss how Viagra could save marriages.
Sexperts have since hailed the move as "like getting the blessing from the Pope" and that it turned sex from being seen as for "naughty time" to "saving the institution of marriage".
Viagra subsequently hit the shelves in the US and UK in 1998 as the first approved oral treatment for erectile dysfunction.
Famous endorsement
In 2002, Viagra was endorsed by Brazilian football ace Pele. After retiring, he spoke to fans inside Rio de Janeiro's Maracana stadium and said: "Talk to your doctor, I would."
Pfizer's weekly subscriptions for Viagra grew quickly from 500 to 36,000.
In 2008 it became the fastest selling drug in history with annual sales peaking at £1.6billion.
The drug was so popular that it reportedly became the most counterfeited drug of all time.
Dr Irwin Goldstein, Director of San Diego Sexual Medicine, echoed the success of the product.
READ MORE SUN STORIES
Goldstein added: "It created sexual medicine. It allowed the taboo to be broken."
Keeping It Up: The Story of Viagra airs on BBC Two tonight at 9pm.