ubrat Pulev’s a nutter,” Eddie Hearn said as he lowered his voice and leaned forward conspiratorially. Hearn’s fighter, Anthony Joshua, faces Pulev on Saturday night in the first world heavyweight title contest to take place in a bio-secure Covid-19 bubble. The curiously open and engaging nature of boxing, the most brutal and dangerous of all sports, has been even more evident this week as the fighters, managers, promoters, television crews and lowly writers have all been cooped up together in a cordoned-off section of a hotel in Wembley. “He’s scary,” Hearn continued after I told him how Pulev had been a quiet revelation whether talking about books or his father, psychology or his conviction that he will beat Joshua. “Every time I’ve seen him this week I’ve gone like that.” Hearn bunched his knuckles in the traditional fist bump of the fight bubble. “And Pulev’s really hit me quite hard on the hand. Not violently but I’ve gone [Hearn wrings his hand]. I said: ‘Kubrat, can you stop doing that?’ He looked at me and said: ‘Ha, ha, you easy …’” Hearn has hundreds of millions of pounds hinging on the outcome of this fight. If Pulev were to shock Joshua and strip him of his IBF, WBA and WBO belts he will simultaneously rip up Hearn’s intricate plans. An expected victory for the champion, in contrast, would secure a two-fight deal between Joshua and Tyson Fury, the WBC title-holder. Joshua against Fury, an all-British battle for the undisputed heavyweight championship of the world, would be a wild, compelling and insanely lucrative affair. Hearn expects the first fight to secure around 2.2m buys on pay-per-view. Pulev stands in the way – but the Bulgarian’s toughness is not matched by the kind of hand speed which unsettled Joshua when he was stopped 18 months ago. Andy Ruiz Jr, dismissed as a roly-poly no-hoper, hauled himself off the Madison Square Garden canvas to blitz Joshua. The fallen champion looked battered and bemused on that crazy night in New York. It says much for Joshua’s professionalism that he won the rematch in Saudi Arabia last December by opting for a more cautious strategy. He regained his titles with a wide victory on points but doubts remain because Ruiz partied harder than he prepared for that second fight – and memories of Joshua’s vulnerability have yet to fade. Pulev looks lean and confident and Hearn said: “He’s a tough guy. He’s proud. But AJ is in a good place. He’s edgy, he’s nervous, which I think is a great thing because, in these fights behind closed doors, it’s easy to be five rounds in and coast a little. And with 1,000 fans there on Saturday it’s going to be even weirder than having nobody because it’s somewhere in the middle – but still more like an exhibition atmosphere behind closed doors.” The unsettling truth is that this will be the opposite of an exhibition. Robert McCracken, a down-to-earth Brummie realist who has trained Joshua since the amateur days and been in the corner for all his tumultuous high and lows, spoke plainly: “It’s very tough for heavyweight boxers. They are always one punch away from disaster. But Josh’s trained long and hard. He’s taken Pulev deadly serious.” McCracken nodded when asked if he agreed with Hearn’s assessment that Joshua, beneath the amiable quips, is on edge. “He is. Pulev is another top fighter with an unbelievable record – he’s only ever lost to [Wladimir] Klitschko. Very skilled, durable and tough. Josh is up against it because it’s another live challenger. They’re not hand-picked or No 15. It doesn’t work like that with big Josh.” The giant shadow of Fury hangs over the event – even if the 6ft 9in WBC champion with the outrageous suits and outlandish mouth is not expected to accept Hearn’s offer to attend the fight. McCracken was pragmatic again when asked about Fury. “Heavyweight boxing is so dangerous you can’t be thinking of future opponents. You’ve got the mandatory challenger [Pulev] who’s really determined, technically good, physically strong. All Josh thinks about is Pulev. For the last six months really. He’s got to get the job done.” Pulev has a terrific jab – which is so often the key to victory in boxing. But, in the bubble, Pulev revealed even more. He was intelligent and amusing company. “I win all the time,” Pulev said when confirming that he is the Jenga champion in his camp. “It’s very precise, like building, which is my second passion after boxing. I like building, I like designing, I like architecture. From when I was six years old I drew buildings.” Pulev is a proud Bulgarian and he says how much he wants to beat Joshua for the sake of his country and, even more personally, for his late father, Venko. “He was a heavyweight,” Pulev said, “and he loved boxing, like crazy, like a maniac. Before me and my brother were born, he wanted his whole life to have boys who became boxing champions.” Venko Pulev was married three times and he became the father to five girls before, finally, 39 years ago, his son was born. “That was me. He said: ‘Wow! I can’t believe it’. He named me Kubrat which is the name of a very old king in Bulgaria. My middle name is Venko after him. My dad had two passions: boxing and books. He was a maniac about books. We lived in our small apartment and all the walls were completely covered in books, from floor to ceiling. In those socialist days everyone had the same apartment, the same furniture, the same couch. But all our furniture was made especially for books. Ten thousand books in one apartment. Every kind of book. History, romance, boxing.” There was a less literary tone when Pulev spoke of his certainty that, driven by the memories of his father, he would knock out Joshua. The world champion clearly remained the king this week. While he was accommodating, Joshua was tucked away in his own bubble within the larger boxing bubble. He is protected by his management but Joshua understands that he will be alone when Pulev walks towards him in a ring full of jeopardy and uncertainty. “I always say Sunday morning will come, so no rush,” Joshua said with a wry smile when I asked him if the last few days of fight week were the hardest. “We’re here now. I’ve trained hard and I feel more confident than last time [the Ruiz rematch]. In Saudi, there was massive pressure. This one I have had a lot of time to work on everything. But it won’t be a walk in the park because, if I don’t take this guy deadly serious, I’m giving him a chance to beat me.” Joshua had heard all the questions about Fury and their anticipated showdown in 2021. “I’ll give you the answers but please, right now, it’s solely about Kubrat Pulev. My focus is not on anyone else.” In a small huddle around Joshua someone persisted and asked how he felt about Fury choosing not to be at ringside. “I don’t think too much about it. He’s a good fighter. He’s done well. Good luck to him, but Saturday night is my night.” Joshua’s cagey display in the Ruiz rematch was followed soon after by Fury crushing Deontay Wilder to become WBC champion in Las Vegas in February. “Yeah, but remember it took a long time for Tyson Fury to become destructive,” Joshua said. “I’ve been that destructive ever since I started boxing. But I’m just going to do the job against Pulev in the best way possible. I’m ready for a 12-round fight but if a shot lands and causes a lot of damage I will be looking to take him out. Once a killer always a killer. Certain people can’t sleep at night because they’re really tuned up for a fight but I must be a good psychopath because I’m sleeping like a baby.” Boxing’s capacity for tumult soon replaced such tranquillity. Friday afternoon’s weigh-in descended into a flurry of chaos as Pulev shouted at Joshua: “Tomorrow I’m going to destroy you.” Joshua replied: “What? You? Disrespect me and I’ll show you.” The fighters came nose-to-nose while, at the back of the room, Pulev’s vociferous Bulgarian entourage charged the burly line of security men. The scuffling lasted for 10 seconds before the fighters exchanged more insults. “They wouldn’t stop,” Hearn told me afterwards. “In the end Pulev said: ‘I respect you’ and that dampened it. But he started again. Pulev said: ‘Tomorrow I will finish you, I will end you.’ AJ wasn’t rattled. He was calm and cold.” Hearn grinned. “It’s great,” he said, as he imagined the increased pay-per-view interest in a previously respectful contest. Late on Saturday night, when the bubble darkens, the black lights of the ring will frame the contrasting figures of Joshua and Pulev. All this week’s edgy laughter and noise will die away. Everyone will pause as we wait to see the heavy blows land and discover whether the heavyweight money-spinner between Fury and Joshua has been ruined or secured. Joshua v Pulev is live on Sky Sports Box Office