When Harry Sellers was asked to go on Love Island this year, he was acutely aware of the potential benefits, and the risks. “My modelling agency said it could be good – but it might all go very badly and potentially ruin my career,” says Sellers, 23, a London-based business school graduate and fitness trainer at Barry’s Bootcamp. He knew he wouldn’t have any control over the editing process, and so he “ummed and ahhed” about whether to go on the ITV2 reality dating show, before having a long conversation with his mother. In the end he decided: “I don’t want to be that guy who goes on Love Island and promotes tooth-whitening products and does club appearances for the rest of my life.”

What does he think the producers are looking for? “Worryingly, it’s obviously a person who looks like me – which is probably why I’ve been asked three times,” he says. “People have a perception of me that I’m a classic lad and a love rat because I stay in shape and I’m a model. The phrase: ‘Don’t judge a book by its cover’ comes to mind. Although I project a certain image on Instagram, it’s very much for my modelling.”

Harry Sellers: ‘It might all go very badly and potentially ruin my career.’ Photograph: Jill Mead/The Guardian

Last month it was reported that more young people applied to appear on the latest season of Love Island than applied to either Oxford or Cambridge (23,521 people classed as “domiciled” in the UK applied to Oxbridge colleges last year). ITV says 104,000 applications were submitted from across the country to be a contestant on the show, which prior to its 2015 revamp had a celebrity format. But the casting process isn’t necessarily quite as open as those figures might suggest. While forms were being fired off by fans, a team of producers were trawling Instagram and nightclubs across the country for potential cast members.

Love Island, a constructed reality TV show, thrusts a collection of twentysomethings into close quarters in a Mallorcan villa for about eight weeks. During that time, the contestants are given the task of pairing up, going on staged “dates” and strutting around in beachwear. Every week, the public vote on which couples they want to boot off, while opportunities to recouple also arise, which can lead to some animosity when contestants leave their lover for another islander – right in front of them.

Since the relaunch, the series has ballooned in popularity, tapping in to modern-day dating culture in a social media-friendly mix of soundbites, high drama and beauty, while providing viewers with an outrageous form of escapism that may be more in demand than ever before.

The producers told talent agencies that they specifically wanted people looking for love this year – not wannabe celebs, or anyone not genuinely seeking a partner. They wanted heartsick singletons ready to fall for someone: the perfect contestants, in other words, for a show where glamorous twentysomethings variously enjoy and endure the tribulations of life within a face-to-face Tindersphere.

The final cast now appearing on TV is split pretty much 50:50 between people who applied and those who were approached.

Perhaps surprisingly, given the appeal of a free holiday, a potential love match – and the possibility of making significant sums of money after appearing on the show – plenty of people said no.

ITV says its net is cast as wide as possible in an effort to find people from as many walks of life and backgrounds as they can. Conscious that viewers are predominantly 16-34, the producers ask themselves: what would be their dream holiday? “We wanted to have a villa that would be their ultimate place to visit and a cast of people that represented our audience, but was also an aspirational version of them,” says Richard Cowles, ITV’s creative producer. “Clearly the contestants are extremely attractive – they have to be for the format to work – but we’re not saying the whole world looks like that. It is an aspirational show. We’re not trying to pretend this is reality. This is a sort of hyperreal world. Normal life doesn’t always look like this, nor should it. But what is refreshing, and engaging, is that these sorts of hot people share all the same insecurities and issues as we mere mortals do.

Some of the contestants on this year’s Love Island. Photograph: ITV/Shutterstock/Rex

“The truth about love and emotions is that there’s always a risk, even if you’re drop-dead gorgeous – that someone hotter, funnier or more engaging might walk in and upset things.”

The contestants all conform to a narrow body type – hunky men and slim women – and it has been criticised for its lack of ethnic diversity particularly when it comes to women. Cowles recognises that there are always ways the show could do better, but says he hopes people do feel that there is diversity, and that “there are people in the cast that reflect them and their place in Britain”.

One apparent requisite for anyone who appears on the show is a thriving social media presence - something that would have been unfathomable when Big Brother began the reality-show era in 2000 – social media didn’t exist then, after all.

“Most of the contestants already seem to have a social media following,” says an ex-talent scout from a leading reality TV show. “That is what has changed in the last two to three years – you used to do a bit of a stalk on Facebook and Instagram, but it has become so much more important now as the show has become more elitist. Who you’re friends with matters, but now it has become much more of a thing than it was.”

Benji Rom, an agent at Roar Global, a leading talent management group, says producers’ main aim is to create the best TV show possible, rather than trying to create romantic matches, and as such will recruit the best candidates no matter where they are found.

Given the number of London-based models on the show this year, model Dominique Sapsin says joining the cast would defeat the object of trying to find love – she already knows many of the contestants taking part. “It’s a running joke between me and my friends; we’re all wondering who will be next,” she says. “Most of the people on the show are friends of friends. They’ve clearly approached these people rather than picking people who have applied. My friends all joke about it and say: ‘OK, next year I’ll do it as a last resort’ if their careers don’t pick up. In theory, it would be hilarious to go on the show, but I couldn’t bring myself to do it.”

In what was derided as evidence that the show is a “fix” it emerged that Megan and Alexandra, a new arrival, knew each other prior to their TV meeting but failed to mention it, corroborating Sapsin’s friends-of-friends comments.

“There are long-term effects of being on TV,” she adds. Contestants, both past and present, have had revenge porn containing explicit images of them posted online and received death threats.

Sophie Gradon, who died in June. Photograph: ITV/Shutterstock/Rex

The trolling of contestants was brought into horrifying focus earlier this summer with the death of Sophie Gradon, who appeared in 2016. The former contestant had spoken openly about having anxiety and depression, and an inquest into her death is ongoing.

Before she died, the former contestant had spoken of being in a “dark place” because of the “amount of negativity focused towards me” from online trolls. Her partner killed himself several weeks later.

After her death Calum Best, the winner of the first series, stressed the need for support for contestants after they leave. As much fun as the show can be, he said, “people need to make sure that people’s minds are right. Whether that’s viewers or the people on the show, we need to make sure there is support and monitoring.”

Gradon’s boyfriend had expressed his concerns in a social media post where he warned people of the potential dangers of being in the public eye. “They see a claim to fame,” he said. “They don’t see that in 10 years’ time, when you’re married with babies, you’ll still be haunted for the rest of your life.”

The show’s producers say they have robust systems to safeguard people and that their casting team stay in contact with people long after they leave. “We do make people understand that this is potentially a life-changing experience,” a spokesperson said.

Jordan Grace, a popular model and a DJ, also rebuffed the producers, aware of how difficult the backlash can be. “I couldn’t have gone on it, knowing the nation is posting stuff on social media about me, and not have any contact with the outside world,” he says. “I’m self-conscious enough.”

Jordan Grace, who turned down the offer of appearing on Love Island Photograph: Graeme Robertson/The Guardian

He says he went to the Henley Regatta with a friend who was on last year’s show; while there, a visibly aggrieved member of the public called his friend “a cunt”. This year, the family of the contestant Eyal Booker have received death threats after he was said to have slighted another contestant. The Daily Mail promptly followed up with a piece titled: “15 reasons why Eyal is the nation’s most HATED reality TV star since Nasty Nick” as insults flooded in on Instagram.

Will those who appear this year – their every action immortalised online – regret it? It is common for ex-islanders to earn six-figure sums in the year after the show. Clubs will pay thousands for former contestants to attend events, while sponsorship and modelling deals beckon.

Rom managed Montana Brown, a contestant in 2017, who was originally approached in a club to go on the show. “It has catapulted her into the limelight and it has given her a new career – so if that’s what you want to do I would say 100% go for it,” he says. “I think there’s always a risk when you’re going on to one of the most-watched TV shows. You’ve got to be so careful about what you say, what you do, your actions towards people and even the looks you give. You have to be aware that you are being filmed 24/7 and nothing will go unmissed.”

Now that they have seen this year’s series unfold, do those who said no to Love Island regret their decision? “Not at all,” says Sapsin.

Grace, meanwhile, says the way the series is panning out has made him “even more happy” he said no. “It’s got worse and worse,” he says.

This year the show has even embraced the relentless culture of scrutiny the islanders experience on social media. In a bizarre game of Twitter “bingo”, contestants were forced to fill in the blanks of tweets posted about them online. “BLANK and BLANK are actually into each other. BLANK and BLANK are like brother and sister, no chemistry,” said one tweet that sparked chaos in the villa.

“The first few seasons were reality TV but now they manipulate it more and it has become darker as they introduce people’s exes. It’s brutal,” says Grace.

In the UK, Samaritans can be contacted free from any phone on 116 123. In the US, the National Suicide Prevention Lifeline is 1-800-273-8255. In Australia, the crisis support service Lifeline is 13 11 14. Other international suicide helplines can be found at befrienders.org