Patrick Hyland, a gentle and amusing former boxer who once called himself The Punisher, waits for the boys and girls he now trains at the gleaming Straight Blast Gym in Tallaght, Dublin 24. An empty ring sits in a far corner while, to his left, the MMA cage is also silent on a sleepy afternoon. It will be another hour before the chattering kids who dream of becoming boxers or UFC fighters tumble in to work with Hyland and the mixed martial arts trainers.

Facebook Twitter Pinterest A mural of Conor McGregor in the gym where he trains in central Dublin.

They all know that the distinct worlds of boxing and MMA collide in Las Vegas on Saturday night. It is a surreal boxing match which has little else but money wedged deep in its murky heart. Of course Hyland’s tiny scrappers also know that Conor McGregor, from down the road in Crumlin, Dublin 12, will earn around $100m for his professional ring debut. McGregor, a brilliant showman and the intelligent fighter who dominates the UFC, faces Floyd Mayweather, a masterly defensive boxer.

Mayweather is coming out of retirement for an even larger payday and the expectation that he will outclass a novice and lift his record above the great Rocky Marciano to a 50-0 mark which would be perfect – but for the absurdity of an apparent mismatch.

The 33-year-old Hyland approaches the sporting melodrama differently by mixing humour and pathos. He met John Kavanagh, McGregor’s coach, at a party in 2013. “We were having a bit of a laugh, a few drinks and we were yapping away and agreed that I’d spar with Conor.” The first session was a jokey MMA and boxing mishmash and when Hyland was kicked in the leg “it felt like someone shot me with a big bazooka”. But then in 2015, he gave McGregor his first taste of elite-level boxing.

Facebook Twitter Pinterest Patrick Hyland, in his gym.

A friendship formed between two contrasting Dublin fighters and Hyland remembers how McGregor tried to console him after the death of his father. Patrick Hyland Sr killed himself in June 2015. He had always been in his son’s corner and Patrick was devastated.

“Conor contacted me when my father died,” Hyland says, “and I told him exactly what my dad thought of him. My dad always said: ‘McGregor’s the new star’ and that Conor reminds him so much of Bruce Lee. My dad was a Bruce Lee fan but he didn’t like Conor’s attitude. He was a boxing man and he said: ‘His attitude stinks. I’d say it to Conor’s face if I see him.’ Conor laughed and said: ‘Listen, he’s not wrong. Bless your dad. I’m sure he would have knocked me into shape.’ It was a good laugh.”

Hyland understands boxing far more intimately than most who, like me, have dismissed Saturday’s event as a farce. Only last year, having lost only one contest in 32 fights, Hyland was good enough to challenge Gary Russell Jr for his WBC world featherweight title. Hyland tells some very funny stories about being knocked out by Russell but he is serious when assessing McGregor’s boxing credentials.

Conor McGregor: from Dublin plumber to UFC champion – in pictures Read more

“The second time I went down to spar Conor at his new gym [on Dublin’s Naas Road in 2015] he was very good, very snappy. We sparred for 20 minutes and he held his own. He had a bit of weight on me but I was letting my punches go and he was taking them, moving, picking me with a jab, southpaw coming in with the left. He made me miss. He could box.”

Everyone in MMA extolls the power of McGregor’s left hand. Did he hurt the smaller Hyland? “I’ve been boxing all my life so I’m used to taking shots. He had a bit of a pop. When it landed you felt it. I didn’t mind it with a 16oz glove and headgear. But I don’t want to be hit flush with an 8oz glove by Conor. So, just like in MMA, Conor should come straight out, no fear and have a go. But he needs to throw at least 100 punches a round to get Mayweather out of his comfort zone. How do you do that? But Conor is a genius so maybe he can. Everything he says, he does. It’s amazing.”

Hyland smiles when I tell him about my lunch with McGregor’s father. Rather than meeting in Crumlin, the working-class neighbourhood of Conor’s childhood, or the more salubrious suburb of Lucan where the family moved when he was a teenager, Tony McGregor suggests lunch at the plush Westbury Hotel. McGregor Sr, dressed up to the nines, launches into a story about how he has just taken his son’s lavish yacht on its maiden voyage across the Irish Sea.

Conor’s yacht has the Italian style, the polished veneer, the wood, the cream leather, the chrome. It really is fabulous Tony McGregor, Conor’s father

“Conor’s yacht has the Italian style, the polished veneer, the wood, the cream leather, the chrome,” McGregor Sr says. “It really is fabulous.”

The yacht is called The 188 – the amount in euros Conor received on welfare right up until the week of his first UFC fight in April 2013. McGregor Sr, who drove a Dublin taxi for 26 years, has just completed his “skipper’s course” so that he can sail The 188 whenever he likes.

“I’ve had a few meaningless jobs over my time,” McGregor Sr says, explaining he was a hospital orderly when Conor was born 29 years ago. “I’m 58 so I’ve chopped and changed. But I loved the taxi driving. I worked most nights and I had great fun with the people of Dublin.”

Beyond sailing, McGregor is planning to fill his retirement as a part-time celebrant who can marry couples in a civil ceremony. So life has changed beyond recognition and McGregor surveys the Westbury in wonder: “Look, apart from us, it’s just ladies who lunch. Incredible.”

McGregor soon celebrates his favourite boxing photograph – in which a towering Muhammad Ali shouts “Get up and fight, sucker!” over a stricken Sonny Liston in 1965. “We still have a copy hanging in the utility room and it’s quite possible Conor could be standing over Mayweather in a similar stance. Mayweather’s evasiveness and defensive fighting will not stop Conor. His left hook has phenomenal power. People call this a mismatch but it’s in our favour. Age, size, weight, power. We’re 100% confident. Conor is going to blow boxing to smithereens.”

Play Video 1:04 Conor McGregor: 'I'll bang Floyd Mayweather out and play with him after that' – video

That positive conviction did not feature when McGregor considered his son’s future 10 years ago. There were raging arguments as Tony tried to persuade Conor his ambition of fighting in the UFC was a ludicrous fantasy. He needed a trade – and so Tony and his wife Margaret worked hard to find their wayward son a plumbing apprenticeship.

“That was me being a parent,” McGregor says. “One of Conor’s teachers told us he had the intelligence to be a lawyer but he didn’t have the interest. I put a proposition to Conor. I’d give him €10,000 if he went to college. He didn’t take the bait so I was concerned. I’d never heard of MMA before. I’d come in after hours and Conor would be watching UFC with his girlfriend Dee. I’d watch a few minutes while I was winding down after my nightshift. But the two of them were engrossed in this combat sport.”

Conor McGregor once told me: “I had no love for plumbing. But it’s weird how society works. Rather than allowing you time to find the thing you love and can pursue with complete conviction, we’re told: ‘You must work – no matter how much you dislike it.’”

What are his father’s memories of those plumbing days? “It was very difficult to get him to the site in the foothills of the Dublin mountains. It was cold, wet, miserable. He would come home and it was obvious he had no interest. I’d throw him money, because as a taxi driver I had ready cash, trying to keep him motivated. We did this for a year and got him up every morning. I’ll never forget one Monday morning I said: ‘Conor, it’s time for work.’ He peered out from under the duvet and said: ‘Look, it’s not for me.’ I closed the door and said to Margaret: ‘He’s never going back.’ It was pointless.”

Facebook Twitter Pinterest Paddy Holohan training the kids at his gym in Tallaght.

His son had immersed himself within the fighting camp run by Kavanagh – who still trains McGregor and will be in his corner against Mayweather. Kavanagh and a tight-knit community of MMA fighters – Owen Roddy, Aisling Daly, Paddy Holohan, Chris Fields, Cathal Pendred and Tom Egan – were eventually joined by McGregor who left the Crumlin Boxing Club to explore his deeper interest in mixed martial arts.

Holohan, McGregor’s friend and the magnificently-bearded former UFC fighter who was forced to retire last year, runs his own Straight Blast Gym in Tallaght – a new centre, not far from Hyland’s gym, specialising in MMA. After an hour-long lesson tutoring 60 teenage boys and girls, he remembers McGregor’s arrival in 2007: “I met Conor in Rathcoole at John’s SBG. He had boxing shorts, a crazy haircut and a boxer’s angry face. Most boxers have that face. Conor was there to compete, he wasn’t there to join a family atmosphere. But after a spar or two, and some serious grappling, he realised we’re helping each other.”

McGregor has always kept a small circle of trusted friends around him. Many from those earliest days remain, either at his side in Vegas or, like Holohan and Daly, in Dublin whenever he returns home. But, before that bond could be made, McGregor went out of his way to make a violent statement.

Facebook Twitter Pinterest Aisling Daly in her gym. Photograph: Paul Faith/The Guardian

“He sparred Owen Roddy first,” Daly says as she pushes her glasses up the bridge of her nose and smiles at the memory of McGregor’s opening day. Daly was an early star of Kavanagh’s gym and, as a woman, she was a pioneer and inspiration in Irish MMA. Her love of fighting, despite being so calm and thoughtful and having to retire earlier this year after a brain scan, is obvious. “I remember Conor hit Owen really hard in the head and made him wobble. John was thinking: ‘Who is this guy? What does he think he’s doing?’”

Kavanagh, trying to dilute the intensity, asked McGregor to spar Daly. She was used to fighting men and was not intimidated. “Conor sparred really hard,” she says, “and dropped me with a vicious body shot. It must have really been a tough shot for me to go down. John had seen enough. He was like: ‘Conor get your MMA gloves on.’ John took Conor down straight away and dominated him on the ground. He didn’t do anything horrible like hitting him in the head but he softened up his body – wiping the breadbasket with nasty little shots to show Conor what it meant. ‘You want to do MMA? Well, this is MMA.’”

The next time Daly and McGregor sparred, she remembers, “I could maul him. At that stage I probably was a purple belt training in jujitsu for four years and Conor was a new white belt. It was easy to control him. He was obviously tough and strong but I may have choked him.”

Conor sparred really hard. And dropped me with a vicious body shot. It must have really been a tough shot for me to go down Aisling Daly

Facebook Twitter Pinterest Aisling Daly in action against Ericka Almeida during UFC Fight Night in Dublin. Photograph: Sportsfile/Corbis via Getty Images

Daly laughs demurely when asked if she had taken offence to the way McGregor had hit her? “Not at all. I was used to guys with egos because some of them think: ‘I’m not going to be shown up by a girl.’ Sometimes you had the opposite: ‘Oh, I can’t touch you!’ – like you were made of glass. Conor gave me more respect. He fought me like I was any other fighter.”

McGregor is a serious fighter who works obsessively hard to improve his skills. Daly and Holohan believe such discipline was forged in their camp from 2007 to 2013. “Some people attribute their success to John, some people attribute it to the team,” Daly says. “We all had the same driven goal and were very close – like a family in terms of we’d eat together, train together and socialise together. We were living and breathing MMA.”

Holohan and McGregor signed on while training six hours a day. Was Daly also claiming welfare? “No. I worked part-time in a shoe shop in town. MMA doesn’t have crazy early-morning starts so most of the time we wouldn’t start training until 1pm. I was lucky with some morning shifts at work. People in the shoe shop would say: ‘Ais is a bit weird. It’s crazy what she does.’ When things took off and UFC became a big deal it was like: ‘Oh, so that’s what she was doing!’”

Daly was amused by McGregor. “I grew up in Drimnagh, he grew up in Crumlin and so we’re from similar areas. He was [six months] younger but there were girls I went to school with and hung around on my street that were Conor’s age. He thought he was a smooth talker. There’d be stories of three girls in a group and Conor might be trying to chat up all three at the same time. ‘Did he say that to you too? He said that to me!’ When girls talked they’d say: ‘Conor McGregor? You wouldn’t go near him!’”

Dublin really does form you. Dublin is a mean little city sometimes. Banter, as we call it, gets flung from an early age. If you don’t know how to handle it you’ll sink

Daly and Holohan’s memories are a credible antidote to the way in which “Conor McGregor’s Dublin” has been mythologised recently to an unrecognisable pulp. There has been much mirth in Dublin over ESPN’s cover feature on McGregor’s past where Wright Thompson, usually an authoritative witness and a fine writer, seemed to have been suckered into melodrama. Some colourful talkers spun him a few old-fashioned yarns about drugs and gangs and how, according to Thompson, Dublin is a “clannish, parochial place. Crossing the wrong street has traditionally been reason enough for an ass-whipping. Men have had to drop dates off at bus stops instead of walking them all the way home.”

Amid the wise-crackers who wish me the best of Irish luck as I head for “the projects” of Crumlin, people seem to feel like Daly did towards ESPN’s exaggeration of Dublin’s problems. “I read a bit of the article and had to stop. It was not in touch with reality. But this will show you the impact of Conor. My mother’s 61 and she was down at our local shops – which is like the Rovers Return and the centre of all gossip. She said: ‘I was talking to the women down the shops and they were telling me about this McGregor article being a load of rubbish.’”

Holohan strokes his ginger beard sagely when I ask him if, beyond such bluster, Dublin has left its mark on McGregor? “Yeah. Dublin really does form you. Dublin is a mean little city sometimes. Banter, as we call it, gets flung from an early age. If you don’t know how to handle it you’ll sink. You had to have a thick skin when we were growing up. There’s a special thing in Dublin, in Ireland, and that wit leaves its mark on us. But I’m cool wherever I walk in Dublin. I’m down with the good people and the bad people. Both sides respect you just being yourself. I don’t take no shit.”

He laughs with the warmth of a man who has just spent an extra 20 minutes helping his gym kids learn how to grapple once their allotted hour is up. It’s also plain that Holohan had a harder upbringing in Tallaght than McGregor did in Crumlin. “But if you asked me to go back again, I would,” he says, “because it made me who I am. I grew up in a council estate 10 minutes from here. I had a single-parent household, but a lot of kids I grew up with are also tough little motherfuckers.”

In contrast both McGregor’s parents were much more actively involved in their son’s life – especially after they rescued Conor in the wake of a humiliating early loss. In only his third fight, as a lowly-paid professional, McGregor was forced to submit after a minute by Lithuania’s Artemij Sitenkov. The shock of the defeat was deepened by the embarrassment of losing in Crumlin – where McGregor was such a big talker.

“I was there,” Daly remembers. “Sitenkov is super-tricky and renowned for his leg locks. It was a fight too soon for Conor and he was devastated. He was gone for the next six months.”

McGregor refused to go to the gym and, as he told me in 2015, he needed his mother to intervene. “My mother rang John when I was drifting. John came to the house and got me back on track. My mother has done so much for me. I can’t even put into words how much I love her. I miss her and my father dearly.”

He was talking in Las Vegas that day and on Wednesday his parents will fly to the same city to watch his $100m boxing debut. It seems hard to believe – even for Tony McGregor. “We’d never seen that business acumen a few years ago – or the showbiz persona.”

Play Video 2:33 Mayweather v McGregor: the Money Fight explained – video

Daly also sounds incredulous when remembering how quickly the McGregor juggernaut has moved since 2013. “It’s bizarre when you look back and realise I was far more famous than Conor. If you thought about MMA in Ireland then you’d say something like: ‘Oh yeah, that’s the thing the girl with the pink hair does.’ Because, in Ireland, MMA meant Ais the Bash or whatever my name was. I did all those TV and radio shows and Setanta Sports made a documentary about me that was shown repeatedly for a year. I definitely felt at the beginning Conor would look up to me in terms of my experience and maybe ask a question or be super-supportive. I was the highest-graded jujitsu person on the team and he was intrigued by grappling.”

Those grappling skills will be redundant against Mayweather – and Daly is more measured than McGregor’s family when assessing the fight. “I really do feel Conor has a chance. He’s 29, Mayweather is 40. Mayweather retired two years ago while Conor has been training and competing all that time. He has been working towards this fight since last year and he is much bigger than Mayweather – and hits much harder.”

Holahan is more strident. “I think Conor will win. Conor is going to shock the whole world. I don’t normally voice my opinion on his fights but this is different. This is going against people who say MMA is barbaric – that we’re uneducated and stupid. Conor will shock them all.”

When I ask Holohan if any of them mind not making the kind of money their former training partner is earning, he shakes his head. “At what price? If you asked me would I take Conor’s life tomorrow, I’d tell you no. It’s a hard life. I could not handle Conor’s life. But he can. And he can handle Mayweather.”

The next day, on the way back to Tallaght to see Hyland, I drop by the Crumlin Boxing Club where McGregor first learnt to fight. Paul Hayden, one of the trainers, leans out of the ring in cheery fashion. His 15-year-old son William, with whom he has been working, has just won gold at the European juniors in Croatia. Hayden is a big, tubby man who loves boxing – and he has misgivings about McGregor: “I don’t like the vulgar or arrogant things he says. Would I like my daughter to be going out with Conor McGregor? No! But he’s a brilliant businessman and a product of Crumlin Boxing Club – so we have pride in him.”

I don’t like the vulgar or arrogant things he says. Would I like my daughter to be going out with Conor McGregor? No! But we have pride in him” Paul Hayden

Facebook Twitter Pinterest William Hayden, 15, has just won gold at the European junior boxing championships in Croatia.

Hayden grins and explains how, in the early hours of Sunday morning in the club, they will screen the fight: “It’s going to be packed.” Does he want McGregor to win? “Well, I don’t like Mayweather at all. So it’ll be bitter-sweet whatever happens. If Mayweather loses it won’t look good for boxing. And if he wins a part of me will be sorry. Conor is from Crumlin. He’s one of us and what do we always tell the world? You can never beat the Irish!”

“Conor McGregor’s just an Irish kid, a boy from Crumlin, and he’s conquered the USA. He can inspire anybody. He’s an absolute machine. How can we not want him to win?”

Hyland is emphatic. “Of course boxing means so much to me, and it did to my dad, but I’d love Conor to win. I’m flying to New York and then the day of the fight we’re driving down to New Jersey. We’ve rented a house on the beach so we have a load coming over from New York for a Conor McGregor party. Some people say he’s not a role model because of the way he talks. But the kid was on social welfare and had nothing in life. He had a goal to be a millionaire and a UFC champion. Now he’s a UFC double champion and making millions.”

Hyland is a boxing man to the core but, even more deeply, he and McGregor are from Dublin. He smiles helplessly – thinking of their sparring sessions and exchanges following the death of his dad. Hyland says a few more words just before the boxing boys and girls burst through the door. It sounds as if he’s speaking for all of them and most of Dublin: “Conor McGregor’s just an Irish kid, a boy from Crumlin, and he’s conquered the USA. He can inspire anybody. He’s an absolute machine. How can we not want him to win?”