"I love these two wee fellers," a tall man says with drunken solemnity as he gazes at Barry McGuigan and Carl Frampton on a sunlit afternoon in Tiger's Bay, Belfast. Outside 9 Upper Canning Street, the small terrace where Frampton grew up before he became a professional boxer and the natural successor to a fighting icon in McGuigan, the drunkard and his chubby pal pay homage to their heroes. Their woozy adoration is as obvious as the bare rolls of fat hanging over the shorter man's trousers. In intoxicating detail they try to tell the two fighters how much they mean to everyone in Belfast.

After 30 years of fame McGuigan displays an easy grace. He listens patiently while hearing how their fathers shed tears of salty pride over him in the ring in the 1980s. In the fiercely loyalist territory of Tiger's Bay and, just a block away, in the republican neighbourhood of New Lodge, the same cry of "Leave the fighting to McGuigan" echoed across these divided communities as sacrilegious violence was replaced, briefly, by united support for the world champion featherweight.

McGuigan now manages Frampton, the super-bantamweight who, on Saturday night, will fill the Odyssey Arena with 8,500 fevered souls from every corner of Belfast as he faces Jeremy Parodi in an IBF world title eliminator. The Frenchman has a commendable record of 35-1-1 but Frampton, who has won each of his 16 bouts, faced greater adversity in Tiger's Bay.

"He's a lovely kid," McGuigan says. "Carl comes from this area where your territory is marked. There have been many horrible things said to him but he's had the equanimity not to be involved. While I spent loads of my life in Belfast it was easy for me to stay separate and look at it from the outside. Even though I lived in a republican town [Clones] it wasn't as severe or nasty.

"Carl lived here right on an interface where houses still have 30ft-high metal fences to protect them from petrol bombs. When you live on the interface it's terrifying but he hasn't allowed it to affect him at all. He's going to marry Christine a week after the fight – they're very mature about their future. Carl comes from a hardened loyalist area and Christine comes from a hardened republican area. And they've risen above it all. Christine is a beautiful girl, really sensible, clever, bright. This is the next generation."

As Frampton ambles down to the bottom of his old street, to sign an autograph for a passing schoolgirl, it's hard to forget the story he told me a few weeks ago at his training camp in Battersea, in a chic corner of London. Frampton and McGuigan's son, Shane, his 24 year-old trainer, have been working relentlessly for the past 10 weeks towards this fight.

In Battersea, on warm autumnal days, they sometimes rolled up the metal shutters to Shane's gym so that it was possible to see Vivienne Westwood's and Victoria Beckham's studios around the corner. And it was there, in a pristine London gym, that Frampton reminded me how he had lost a close friend, Glen Branagh, in another tragic moment of the Troubles on Upper Canning Street.

Branagh was 16 when a pipe-bomb killed him in 2001. Frampton was 14.

Boxing saved Frampton from joining the wild thrill of sectarian violence in an area where, amid desolation, it is difficult to hold on to hope. "I saw a lot of trouble," Frampton said after a long day of training. "There was a lot of danger. People died. One 11 July, Bonfire Night [in loyalist Belfast], a good friend of mine was shot. They fired into the crowd and my friend got hit in the stomach. It was obviously worse in Barry's day. I grew up on the back end of it but it wasn't nice.

"In Tiger's Bay I saw trouble I shouldn't have seen. But 95% of the people there are good and they're coming out to support me – just like in New Lodge which is the opposition or whatever you want to call it. As a kid I could be in New Lodge in a minute. I'd go down our street, turn right and I was there."

Carl Frampton during training at Shane McGuigan's gym in Battersea. Frampton will fight Jeremy Parodi on Saturday night. Photograph: Tom Jenkins/for the Guardian

I listened closely to Frampton in Battersea for, despite his amiable wit, he already has the commanding poise of a great fighter but it is only here, in Belfast, that I really appreciate the extent of his achievement – and the way in which his unifying path towards a world title follows the pioneering route mapped out by McGuigan at the bloody height of the Troubles.

"When I went through it we were right in the throes of a spiteful, murdering campaign from both sides," McGuigan remembers. "It was horrible and awful. You tried your best to ignore it but it was everywhere. There's a saying over here – "Catch Yourself On" – in other words "Be Real". The reality was that you were walking around a war zone. It was proper scary stuff."

In June 1985 20 million BBC television viewers watched McGuigan win the world featherweight title against Panama's Eusebio Pedroza, who had been the WBA's champion for seven imperious years. His fame was accompanied by a heightened sense of danger. McGuigan describes how closely he had been watched for 10 days in 1985 when there were rumours that, as the most celebrated man in Ireland and much of Britain, he might be kidnapped. "It was red alert," he says. "I had plainclothes guys in the north and south. They gave me a gun…"

The 52-year-old, as warm and lucid a speaker as anyone in sport, bursts out laughing as he emulates his ineptitude with a gun. "It was like Blazing Saddles," he roars, closing one eye and firing off an imaginary wayward shot. "It was the time they took Shergar. They were willing to take that risk because at the time I was high and mighty. Kidnapping me would've killed them stone dead in PR teams but it was a massive red flag situation. I said, 'For fuck's sake…,' when they gave me the gun. 'I want to shake people's hands. Not shoot them.'

Carl Frampton during training at McGuigan's gym in Battersea. Photograph: Tom Jenkins

"So we move on 30 years and here we are with Frampton in Belfast. The tension is still here. There have been a number of bomb hoaxes the past few days and the M1 was closed with 25 miles of traffic – a couple of devices had to be removed. So it's still simmering and they say the peace walls are even higher. There has been genuine peace and when you see Martin McGuinness and Peter Robinson together it's heartwarming but the stuff simmering below the surface worries me. In general the two sides have called a halt to violence but we need employment and investment and patience and extra help. This place has had an awful lot of bad times. If we don't get help the bad boys will rise up again. That's what I'm afraid of…"

We spend the afternoon crisscrossing Belfast – beginning at the Midland Amateur Boxing Club where Frampton first discovered his love for the ring. And it is here, outside this deserted gym in Tiger's Bay, where another measure of Frampton's power is evident.

There are still murals all across Belfast and political slogans continue to be daubed on walls that have been painted and stripped and painted over again and again – but this one demands closer scrutiny. It's a mural dedicated to Frampton as a champion amateur boxer and in Tiger's Bay it seems striking that he should be depicted in an Irish vest with a shamrock on his chest.

"In boxing we're allowed to come together," Frampton says, "Protestants and Catholics, the north and south, everyone. I'm in an Irish vest, even on a mural in Tiger's Bay, because boxing brings the communities together."

Frampton is a winningly modest fighter but his pride is obvious as he and McGuigan study the unblemished mural which has never been smeared with graffiti or political slogans. "It's obviously a great honour, even if it's a bit strange seeing a massive picture of yourself on a wall. It's me in my Irish vest with a trophy for winning the All-Ireland title. It's been up a few years now but it would not have happened 10 years ago. That shows you things are changing for the better."

In recent times Frampton has contributed further to this improved atmosphere in Belfast – as illustrated by his two previous fights when he had the Odyssey rocking with mixed crowds united in vociferous support. "Without being big-headed," he says, "I am doing that a little bit. I feel humbled I'm supported by both sides of the community. Barry had that as well. It was a little different in his day but, when Barry was fighting, trouble stopped in the streets. People came together. I'm also bringing people together."

Carl Frampton stretches during training at McGuigan's gym. Photograph: Tom Jenkins for the Guardian

Inside the Midland, as Frampton walks around his fighting home, he remembers how it started. "I was seven or eight and a kid who was easily picked on. Not bullied but other kids would've told me what to do in the streets. I was very shy. I used to put my head down. I was a very sensitive kid but one night I came down here and I was beating the bullies up in the gym –which felt good to me."

New Lodge is a one-minute walk away from his old house on Upper Canning Street but only boxing allowed him to venture into forbidden territory. "I did a lot of training in the Holy Family gym with Gerry Storey in New Lodge but here's the strange thing. New Lodge offered a short cut into Belfast city centre but until five years ago you wouldn't have walked through it – even though I'm involved in boxing. You went the long way round."

On days when he trained at the Holy Family he was free to enter New Lodge. "We also had kids from both sides at Midland. It was the same in all gyms in Belfast. They're all mixed. There is no split between Catholic and Protestant. Everyone trains together."

Over the next few hours McGuigan drives us across the city, moving in and out of notorious zones from the Troubles, to illustrate boxing's extraordinary achievement. A familiar old slogan – "End British Internment" – is daubed across a wall near the Holy Family. Stark high-rise flats surround the gym but, inside, a lightness lifts the mood.

As we climb the stairs McGuigan remembers how, in the 1970s, even British soldiers were allowed into this gym. "In the middle of the Troubles the paras would come here and fight the Holy Family boys. The place was packed with spectators because boxing was different. People didn't give a shit who was in the ring as long as it was a good fight but if they gave the paras a good beating, as they usually did, it was even better…"

In different eras, McGuigan, a Catholic, and Frampton, a Protestant, spent many years in the Holy Family. It seems incredible that boxing brought two warring communities together.

"That was the paradox," McGuigan says. "Peace be with you – and you were punching someone in the mouth. But boxing was an olive branch. Boxing allowed you to do things nobody else could do. It was a horrible time, a terrifying time. It was inhumane. You look back and think: 'Christ Almighty, did our neighbours and friends really do such barbaric things?' But they did. It happened."

McGuigan brightens again. "For many of us boxing was a sanctuary. It was a release, and an education. We travelled the world and met different people. And we became better human beings. Boxing was unique."

The template was secured by McGuigan. "I boxed for Ulster, Northern Ireland and Ireland and did so at a time when you would think it's totally unacceptable. I've carved out a road that I don't think anyone else has been down. But there were never any barriers as far as I was concerned.

"Then, it was all about, 'Yeah, nail your colours to the mast.' I said, 'No.' We weren't going to alienate people and make them feel ostracised or threatened because everywhere you went you felt that – you were looking over your shoulder. But I walked through places that nobody else walked through and was received with open arms. I look back and think 'Holy shit, did I really do that?' I was a kid. But boxing allowed me to do that…"

Leaving the Holy Family we hear something that sounds like gunfire. McGuigan swears, apologises and then laughs when I remind him that I come from Johannesburg. It's a little like being home again – for both of us. We move from the Falls Road, zipping past the black flags and Irish tricolours, to the Shankill Road's union jacks and murals dedicated to the Queen.

"I had a Falls Road and a Shankhill Road Supporters Club," McGuigan says. "It was a special time – despite so much murder."

Inside the Ulster Hall, a beautiful and elegant building, McGuigan's voice echoes as he throws fierce combinations in the air and helps me imagine the steaming atmosphere at a venue where he fought more often than anywhere else. It will be even more raucous in the much larger Odyssey Arena on Saturday night but the ornate old church organ pipes at the Ulster Hall are a reminder that Frampton will follow his fight against Parodi with marriage to Christine a week later.

Carl Frampton and Barry McGuigan pose for a picture in front of the mural of Carl on the side of the Midland Boxing Club in Tiger's Bay. Photograph: Tom Jenkins for the Guardian

In Battersea, Frampton had spoken movingly about how much he missed Christine and their two-and-a-half-year-old daughter, Carla. "It's getting harder all the time. Carla's starting to understand and she's asking where I am. I say my goodbyes the night before and sneak out because I don't want her to cry. I'm feeling a wee bit emotional now, thinking about it. I don't want to be upsetting the child and I feel like I'm doing that sometimes. She's quite good though, on the phone but sometimes she's watching Peppa Pig when I call."

Christine, who has a degree in criminology, comes from a contrasting background. "Poleglass in west Belfast is a completely Republican area," Frampton explains. "The first time we went on a date I was so nervous I ended up getting drunk. I forgot to pay for her food. She still takes the mickey out of me."

Was it hard falling in love with a Catholic girl? "It didn't matter to me but I knew it annoyed some people and it was difficult – especially with me being from an interface area where there was trouble all the time. Now, the wedding is obviously something to look forward to but I'm thinking about the fight. People say: 'What about your face?' Well, the Kiko Martínez fight [which Frampton won on a ninth round stoppage in February] was pretty brutal and I was marked but I was healed by the Thursday – well, that's what I'm telling Christine. As long as I don't get cut I should be OK."

Has he given any thought to his wedding speech? "Um … no. You've just reminded me. It's going to be short and sweet, anyway."

McGuigan laughs. "It's incredible how my life is mirrored by Carl's," he says, explaining how, a week after he beat Chris Eubank's brother, Peter, in August 1981, in Ulster Hall, he married Sandra, whom he is still with happily 32 years later. Sandra is Protestant and Barry is Catholic – in a mirror image of the divide which Carl and Christine overcame. McGuigan was cut in his fight against Eubank and the stitches were only taken out on the morning of his wedding.

Barry McGuigan looking around the Ulster Hall in Belfast. Photograph: Tom Jenkins for the Guardian

"Sandy's much better looking than me," McGuigan cracks, "so it didn't matter. Frampton will come through this fight. He won't be unscathed and he'll have lots of bruising but I'm convinced Carl will win. I don't think there's any stopping this guy. He's going the whole way."

All the McGuigans are involved in this first family promotion of a big Belfast fight. Blain, his eldest son, is the promoter, while Shane and Jake look after Carl in and outside the ring, with Barry as manager and Sandra and even their actress daughter, Danika, involved in public relations and ticketing. Their joint ambition is that the bout will lead to a world title fight early next year – hopefully in Belfast.

"It would be very special," McGuigan says as, beyond the troubled history of this scarred old city, he looks to the future. "It would be hugely important to me – and if we were to do it at home it would be absolutely amazing. Boxing's become a more precarious business but I have every confidence that Carl Frampton will win a world title. And we'd love to win it at home, in Belfast."

To watch Frampton v Parodi live on BoxNation (Sky Channel 437 or Virgin Channel 546) from 7pm on Saturday visit www.boxnation.com.