Lee Selby became Wales' 12th boxing world champion when he beat Evgeny Gradovich for the IBF featherweight title in 2015 [Getty Images]Lee Selby knows the risks, knows the danger.He's already been in the corner for one fight, so knows all too well that bareknuckle boxing is fast becoming as popular as it is brutal.But he also knows his own worth."They offered a great amount of money, which I declined," Selby tells BBC Sport Wales."Then they offered more money, which I declined again, and finally they offered me enough to make me say yes."I'm a prizefighter. I've fought my whole life. The prize is money. If the money's right, I'll fight."It's a similar case for his brother and former British flyweight champion, Andrew Selby, who has himself reached a multi-fight agreement to compete in the sport.How safe is bare-knuckle boxing as it fights for mainstream appeal?Gloves Are Off: The Rise of Bare-Knuckle BoxingSimple maths, in many ways.The sums clearly add up, too, for promoters BKB whose bid to try and take bareknuckle boxing mainstream will have been boosted by securing a four-fight deal for the 39-year-old former IBF featherweight champion, four years after he hung up the gloves.Barry-based Selby is not the first former world title winner to make the same switch. IBF super-middleweight and 2012 Olympic gold medal winner James de Gale has previously fought on a different promotion.In July, former WBC welterweight champ and former Floyd Mayweather opponent turned Hollywood actor Victor Oritz will headline a BKB bill in Los Angeles.By then, 39-year-old Selby will know a little bit more about what he has let himself in for with his BKB debut against Italy's Antonio Rizzo scheduled for 26 June in Cardiff.Bareknuckle boxing is on the rise, with a surge in bouts since the first was sanctioned in the US in 2018. Brain injury charity Headway has previously called the sport "irresponsible" and even boxing promoter Eddie Hearn has called the sport "a little bit barbaric for me", but there is an audience for it and it appears to be growing.And BKB's refusal to take no foran answer from a fighter who defended his IBF title four times before a bloodied defeat by Josh Warrington in 2018, gives a hint to their intention.Indeed, the promotion's chief executive David Tetreault has called Selby's signing "a game-changer" as they look to lean on the credibility of legitimate boxing champions.Something to proveSelby has signed a four-fight deal with BKB, whose bouts take place in a three-sided ring called a Trigon [Getty Images]And yet it still begs the question why Selby would be tempted."It's not all about the money," said the man nicknamed 'Lightning' and who also held British, Commonwealth and European titles. He had combined coaching and punditry since retiring in 2022 on the back of a title-eliminator defeat to Daniel Lemos in Buenos Aires shortly after contentiously losing to would-be champion George Kambosos Jr."There were rumours going around the town (Barry) that I'd spent all my money, but that's not the case I invested well, I've got properties."I came from nothing council house family on benefits and food banks so when I'm offered money to fight, I can't say no. Because fighting's in me."Which gets a little closer to the attraction to look past the controversial status of bareknuckle boxing and accept the challenge.Like many retired boxers, Selby admits to have lost a little "purpose" since stepping out of the ring."I'd be riding the horses, walking the dogs, taking the kids to school being a normal civilian," he says. "But something was missing."Selby defended his title four times but turned to coaching after stepping out of the ring in 2022 [Rex Features]He dismisses the notion of risks as no greater than normal boxing because of the shorter rounds, taking less punches over a shorter timeframe, and gloves doing more to protect hands than heads.But the smaller ring space is just another factor why there are more fights ended by knockout or technical knockout than standard boxing, not to mention a greater risk of cuts. A concern for some, an appeal to others."It's stripped back, the truest form of fighting," he says. "And I've got something to prove."Put to him that holding a world title suggests he doesn't, he replies: "Yeah, but I had pillows on my hands."He's yet to try and pillow-less punch on an opponent but says pad work suggests his punches are "so much faster, so much cleaner".He's yet, either, to receive a bareknuckle punch and admits his sister worries. His father who he calls "a boxing purist" wants nothing to do with the venture. But brother and fellow boxer, 2012 Olympian Andrew Selby, has joined him in making the switch into the three-sided ring known as the Trigon."I've had huge success as an amateur and won the British title in the pros. Now, joining my brother Lee in BKB is a dream," said Andrew."Bare knuckle is the original, no-excuses version of the sport we love. I'm bringing my speed, timing, and heart to the Trigon - and we're both coming for world titles."Lee Selby's only live experience of it to date has been coaching one previous fight but he's been studying and notes that the venue sizes are growing.And just as he knows the risks, Selby is equally clear on his aim."The plan is my debut which I don't want to look past," he says. "But, if I was to look ahead, I'd like another fight and then to fight for the world title, defend it and retire a two-time world champion. 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