Returning to his Ibizan hotel room, the stag notices that his best man is missing. Mike Rutter last saw Luke Rhoden when he put him to bed, after Rhoden suffered an adverse reaction to cocaine and ecstasy. Rhoden’s bed has been made. His shoes are lined up. Knowing instantly that something is wrong, Rutter begins calling his friend. As the call disconnects, Rutter turns around and sees the hotel manager standing in the doorway. His stomach rolls away from him, bouncing like a coin down Balearic cobblestones.

“The last thing I said to him,” Rutter tells me, “was ‘Go to bed and sleep. If you need me, ring me.’ So that was the last time… yeah.” He trails off.

After being put to bed, Rhoden jumped from a balcony. Observers described him as frightened and hallucinating. Police officers, apprehending him, pushed a plastic baton into his neck. Rhoden died. In 2016, a British coroner recorded that the cause of death was asphyxiation caused by the excessive restraining methods adopted by officers, as well as the drugs in his system.

Back home, Rutter got married without his best man. “It was very difficult, to be honest,” he tells me. “It was a different wedding, let’s just say that.”

For a long time, Rutter was haunted by the fact that he wasn’t there when Rhoden died. “I nearly lost everything,” he explains. “Bad depression. Counselling. There was a lot of guilt.”

What happens when your stag do ends in tragedy? The loss spreads outwards, like a blight: contaminating everyone who comes into contact with it. “It takes a toll on the people around you. You end up treating people like shit. Wife like shit, kids like shit, everyone around you like shit.”

All nine men on Rutter’s stag weekend have been affected. “Every single person in the group has struggled,” Rutter tells me. “To the point where one of the lads has moved to Australia. He just had to get away.”

I first became aware of the horrifying trend of British men dying on stag dos when a girlfriend whispered in shocked tones of a man we knew who had gone on a stag weekend. By the time they went to wake the stag up in the morning, he couldn’t be roused. He was dead.

To me, this seemed to be an astonishing and exceptional tragedy, but the more I researched, the more I realised that it was not. Although UK coroners’ courts don’t collate data on whether deaths are stag-do related, at least 30 British men have died in the past decade alone while on stag dos. Others have suffered life-changing injuries. And fatalities seem to be increasing: about a third of deaths over the past decade took place in 2017.

Typically, the victims are men from tight-knit communities: family men, with partners or children. They have steady jobs and often play team sports. Many deaths happen overseas, in stag party hotspots, such as Budapest, Magaluf, Hamburg or Ibiza. Often victims don’t have travel insurance and fundraising pages for repatriation costs are necessary. “Bring Watson home to his family,” reads one. “An amazing guy deserves an amazing send-off.”

The deaths I tracked fell, broadly, into three categories. There’s death by misadventure: often related to alcohol or drug abuse. Men die of heart failure after drug binges that leave them car-jacking vehicles, or they drink so much they die of alcohol poisoning. Balcony falls merit their own sub-category: typically, men try to climb back into their rooms while drunk. One Ibizan hotel, the Pisces Park, is notorious for stag-do balcony deaths – two British men died this way in 2015. The second category is death by suspicious causes, such as Rhoden’s death at the hands of police. Then there’s death by brute bad luck unrelated to stag-do activity: undiagnosed heart conditions, or blood clots.

A covenant of silence, forged in party capitals around Europe, persists around stag dos. What happens on tour, stays on tour. But when men die on stag weekends, silence becomes codified into omertà. People don’t want to talk about the fatalities: interview requests fall on deaf ears.

Sometimes, families are ashamed of the circumstances in which their loved ones died. “You don’t want people thinking bad things about your son,” explains one mother over the course of a tearful phone call.

For others, the grief pounds as strongly as a new hangover. “I hate talking about Paul’s passing – it just makes me too sad,” writes the Racing Post columnist Steve Palmer, whose best man, Paul Bush, died on his stag weekend. Palmer sends me the column he wrote after Bush died. “Returning from Budapest with an empty seat beside me on the plane was a soul-destroying experience. I was due to get married just five days later, something I considered almost impossible… A week after the worst day of my life, came the best.”

I make inquiries, pushing into people’s grief. As I’m writing, news breaks that a 29-year-old Scot named Liam Colgan is missing. Liam is his brother Eamonn’s best man and was last seen in Hamburg’s Reeperbahn district, an area popular with stag parties. When I speak to Eamonn, it’s been two days since Liam’s disappearance, and he’s returning home. He sounds weary.

“I’m beyond worried,” Eamonn says. “It’s totally out of character for Liam to go missing. He doesn’t use drugs or anything like that. Obviously, he was under the influence of alcohol quite heavily, as anyone would be on a stag do. But for him not to have any contact with anyone…”

Eamonn trails off, panic edging into his voice. “He doesn’t have his passport. He’s missed his flight.”

Many cultures have rituals by which boys become men. In Brazil, male initiates to the Sateré-Mawé tribe plunge their arms into gloves full of stinging bullet ants. Afterwards, they are welcomed by the tribe, as men.

Like the men of the Sateré-Mawé tribe, Brits are also expected to demonstrate their masculinity through the complicated and often costly ritual of the modern stag do. Dentist’s chairs – a game where you sit and have alcohol free-poured directly down your throat – were banned in the UK in 2010 as part of a package of proposals aimed at tackling binge drinking. However, they remain popular in many European stag hotspots. In 2013, a British man, Paul Tobutt, died at his own stag party in Benidorm, after playing the game. Sateré-Mawé men suffer trial by venomous ants; British men endure trial by dentist’s chair. Both practices are likely to prove poisonous and painful.

It wasn’t always like this. The modern British stag do as a performance of masculinity exploded in the late 2000s, with the advent of cheap airfares to European capitals – where alcohol is cheap, strip-clubs are plentiful and beer is super-strength. Films such as 2009’s The Hangover captured the spirit of this emerging phenomenon, and reinforced the narrative that a stag do isn’t a stag do unless something stupid or dangerous happens.

“A generation ago, the stag night would have been the groom and some friends down the local pub,” says Dr Thomas Thurnell-Read, lecturer in cultural sociology at Loughborough University. Now, stag dos are a ritual of male friendship. “The stag passes from unmarried man to married man. The cultural urge to mark that transition causes all the hedonistic and ostentatious behaviour you see on stag weekends.”

Reckless behaviour, as well as excessive alcohol consumption, is part of the tradition. “There’s this emphasis on ritualistically punishing the stag for this change of status. You humiliate him with fancy dress and make him get drunk,” Thurnell-Read says.

Above all, the group takes precedence. “Being seen to not be drinking is an affront to the male-bonding ritual, to the idea we’re all in this together,” says Thurnell-Read. During his fieldwork in Krakow, Thurnell-Read witnessed men furtively tipping drinks into plant-pots, rather than admit to the group they didn’t want to drink any more.

I want to know how stag do antics can devolve into dangerous behaviour. In a London pub, I meet 35-year-old Kit. He’s a veteran of more than 20 stag dos. “This is how people can die on stag dos,” he says casually. “When you’re in a group of guys, you regress back to how you were as boys. And there’s an amount of peacocking involved. You’re always egging someone on.”

On a recent stag weekend in Hamburg, Kit witnessed a stag – dressed in a hamburger outfit – climbing a telegraph pole. “We’re chanting: ‘Have you ever seen a burger up a pole?’ So he’s like, fuck it. It’s 30ft and he’s pissed. Everyone’s chanting. Falling from that height, he definitely would have died.”

Kit sips his drink. “But you don’t want to be the guy who spoils it. That’s why no one wanted to stop it being dangerous.”

These often extreme stag dos offer up a romanticised version of male friendship; but by contrast they also result in violence or injury. When masculine ideals are collectively being performed by groups of drunk men, it’s easy for things to go wrong.

James Thorpe, 29, knows this first-hand. After breaking his neck on his own stag weekend in Magaluf in 2016, the former firefighter is now in a wheelchair. “I suppose a little bit of stupidity was involved,” Thorpe remembers. “We’d had a couple of drinks and saw some friends swimming and we were trying to get into the spirit of it, so we went for a swim. I’m not quite sure if I tripped or dived – I can’t remember. But I banged my head on the sea bed and broke my neck.”

Luckily, a friend dragged Thorpe out of the water. “If they hadn’t found me within the next 30 seconds, I’d probably have drowned.”

Since his accident, life has changed dramatically. “Day-to-day stuff is difficult. Getting yourself up is an effort; getting dressed is an effort. I still have dark days, but I’m starting to get my independence back.”

Despite everything, Thorpe would go on another stag do. “I haven’t changed my mind on stag dos,” he tells me. “They do have the potential to get out of hand, when you’ve got that laddish behaviour, a bit of peer pressure and showing off. That’s where they tend to go wrong. But I’d still go on one.” He laughs. “I probably wouldn’t return to Magaluf, though. Too many bad memories.”

Messing around near water has proved fatal for other British stags. In 2015, 24-year-old Dale Joint drowned on his stag do after jumping into the water near moored boats in Salthouse Docks, Liverpool.

“Until it touches you, you don’t really think about it,” his aunt, Gaynor Isherwood, tells me. “In one fell swoop, a night out ends up with this. It’s hard to take in.” After Joint died, Isherwood says, she felt like she’d been hit by a bus – and finally understood what that metaphor means. “He was just larking around with his mates.”

Isherwood feels that not enough has been done to prevent similar accidents taking place at the docks. After we speak, I go online. “The recently renovated Albert Dock area is an ideal place to start any stag night out,” I read.

Not all deaths are down to drunken misadventure. Sometimes, nefarious or criminal factors are at work. “Being in a foreign city tends to make people vulnerable,” Thurnell-Read says. “Especially if you’re in fancy dress. You’re very obvious. If anyone wants to mug or attack some foreigners, they stand out.”

When men die on stag dos, it’s easy for them to be victim-blamed. No Ibizan civil guard officers have been charged with Rhoden’s unlawful killing. “They kicked it under the carpet,” Luke’s father, Norman, tells me. “They said it was a done deal, an accidental death. People think: ‘Oh well, it’s just a stag do, he had too much to drink.’”

Entire economies are propped up by stag-do tourism. When money’s involved, there’s a vested interest in the authorities downplaying deaths. Justice may be a long time coming, or may not come at all.

I speak to David Swindle, a private investigator working on the case of Craig Mallon, killed from a single punch on a Spanish stag weekend in 2012. “Numerous evidential opportunities weren’t pursued,” Swindle explains. “There hasn’t been the level of investigation we’d expect. And there’s a wider issue about a lack of support by the British government for the families of murder victims abroad.”

“I’ve realised that my son’s death was just a drop in the ocean,” Norman agrees. “There’s big money involved. And what’s happening isn’t highlighted enough. As quickly as it happens, it’s forgotten. It’s only the people who were around that remember. I’ll be chatting to people I know, and they’ll say: ‘My boy’s off to Ibiza… Oh, sorry I didn’t realise.’ That’s how quickly they forget.”

It’s a brutal alchemy, when men die on stag dos: a life-affirming celebration combusts into death. Tough questions need to be asked. What is it about our society that requires men to perform masculinity according to rigid protocols that result in physical injury or worse? And why do we laud men for adhering to these rituals? I read one satirical article that sums up this approving spirit: “Prince Harry’s stag do likely to end in at least one death.”

Liam Colgan is still missing. Eamonn returned to Hamburg to search for him. “The wedding won’t go ahead without Liam,” he tells me. “We have to find him soon and get him home.”

While some search for their loved ones, and others fight the authorities for justice, for those left back home, life returns to normal – almost. “Everything changes. It’s a different life,” Mike Rutter tells me. “It doesn’t matter what you do. He’s not coming back. That’s probably the worst part.”

Rutter is back at the boxing gym that he and Luke Rhoden used to frequent. For a long time, he stayed away. “I couldn’t go back. I’m back now. I’ve gone back to boxing, finally. It’s good. Things are good.”

For reasons he can’t even fully understand, Rutter has started racing motorbikes. “Luke always used to say this phrase: ‘Life’s for living.’ And for some reason I’ve started racing motorbikes. I don’t even know why. People say it’s stupid, but life is short.”