With twenty five seconds remaining in the eighth round of his blockbuster rematch with Carl Froch, George Groves did something remarkable.

Froch had just detonated a right hand destined to become one of the most celebrated punches in British boxing history onto Groves's fractionally but fatally exposed jaw. The Londoner went down flat on his back, left leg bent on the canvas, and as referee Charlie Fitch knelt over the stricken fighter it was obvious that Groves was finished. Fitch duly waved off the fight, Froch began to celebrate, and that's when Groves did a remarkable thing. 

He got up. 

He didn't get up very gracefully. He rose to his knees, fell forward, steadied himself using a combination of the canvas and Fitch, and clambered to his feet. Fitch guided him back to the embrace of his corner where Groves rested his head on the shoulder of trainer Paddy Fitzpatrick. His coordination was comparable to a drunk at last orders. His willpower and resilience came straight out of a comic book. 

Groves getting up made no difference to the outcome of the fight but it provided yet another reason to celebrate the knockout itself. The beaten man was OK and therefore the punch that felled him could be savoured free from any shadows of concern or guilt, shadows that would have immediately fallen over Wembley had Groves stayed motionless on the canvas. 

It is the most dramatic moment in sport, bar none. The penalty shootout, the buzzer beater, the Hail Mary pass - none can match the visceral thrill of the knockout and its immediate impact on both the combatants in the ring and the audience roaring them on. Fights, careers, lives can be changed in an instant. One mistake, one punch.     

In his fascinating new book - titled, simply, The Knockout – Sky Sports commentator Andy Clarke examines this most devastating and decisive of sporting denouements. How does it feel to administer a knockout - and be on the business end of one? How does a fighter recover when their greatest fear is realised in the ring? As Clarke notes: "If you box for long enough, you're almost certainly going to knock somebody out and almost certainly going to get knocked out." 

Clarke spoke to some of the most celebrated British fighters of recent years – including Amir Khan, David Haye, Tony Bellew and Carl Froch. He delved into the mindset of these unique men – and found some universal human truths there.  

Square Mile: What made you want to write this book? 

Andy Clarke: The knockout is something that's always really interested me because it's not a defeat like any other.

It's very, very personal. It can be really, really difficult to get past. You'll get the most honest assessment from fighters immediately after the event and then usually within minutes it's changed into something else because they have to sell it to themselves. 

A knockout defeat is the ultimate defeat. How do you get over that? And what does it feel like to knock somebody out? What does it feel like to do that to somebody? Are you jubilant? Are you relieved? It's not necessarily what you might think. I think a lot of the time they're just relieved that it's not them. They're relieved that they haven't lost because the stakes are so high. 

How do you come to terms with a sport where winning and losing can be so extreme? Psychologically, how do you approach it and how do you accept it and how do you be at peace with it? If you box for long enough, you're almost certainly going to knock somebody out and almost certainly going to get knocked out. How does that work?

SM: In the book, you identify two types of knockouts: type-one and type-two. Can you explain the difference?

AC: A type-one knockout is what most people will think of when they think of a knockout. That one punch lands and somebody is knocked unconscious, they're lying on the floor on their back and they're out, they're unconscious, and everybody knows it's over. That's a dynamic that every single person in the world understands and that can happen to anybody. 

The reason it happens is because it's a punch that you don't really see. You either don't see it at all or you don't see it enough, you don't see it coming early enough, and so you're not braced for the impact. Generally speaking, those happen early in the fight before resistance levels have really dropped. Froch-Groves is one of those. That one is unusual in that it happened in round eight - although not much had happened in the fight so they were both pretty fresh.  

A type-two knockout is one of those knockouts where it's deep in a really gruelling toe-to-toe slugfest where they're both knocking the shit out of each other for however long. Both fighters are knackered, resistance levels are really low, and then one of them finds that punch. It wouldn't need to even be that big but it's enough to just wipe out what's left of their energy bar and they're done. Those are the worst ones, actually. They can take a lot more out of the boxer than the type one. 

SM: Deontay Wilder against Tyson Fury in the third fight? 

AC: Exactly. He got knocked down and he counted out but he basically collapsed through exhaustion more than anything - the final punch that Fury hits him with wasn't much. But in round 11 it was enough.

SM: Boxing has been around forever - you open the book with a fight from The Iliad - but social media is perfect for sharing a knockout punch. 

AC: It's absolutely ideal for that. I don't know whether social media makes it better or worse for fighters. You get knocked out and it's all over social media and it's absolutely humiliating - what they fear more than anything else is the embarrassment and the humiliation.

But if you've grown up in that space - which more and more boxers will have done - you're more used to the idea that whatever happens will be out there. People are aware that this is what happens in my sport; it's spectacular but not exactly unusual. That can maybe make it easier, I guess it just depends on what kind of person you are. 

But it is the absolutely perfect thing for social media because you don't watch and think, 'Oh, I wonder what happened after that.' Well, nothing happened after that. It was over. A few seconds, bang, done. 

SM: You cite Froch-Groves II as a perfect knockout for a variety of reasons: the magnitude of the event, the rivalry, the punch itself - and also because Groves immediately recovers. I thought that showed an interesting dichotomy.  

AC: It's odd because you do want to see knockouts and it's pointless for anyone who's into boxing to pretend they don't want to see knockouts. It's not the only reason I like boxing but it is the ultimate thing. But if the fighter's just lying there not moving then that wave of adrenaline gets replaced by concern or guilt really quickly.  You want to see it but then once it's happened, you almost immediately kind of wish you hadn't seen it.

SM: It's such an immediate moment for the spectator as well as the fighter. You go from bloodthirsty member of the mob to concerned citizen in an instant. 

AC: It doesn't make any sense, does it? And for a fighter, it's absolute fractions. George Groves said, a fractional error and it's a lifetime work down the toilet. It almost doesn't seem fair that you could be punished so brutally for one slight error, the kind of error you probably make quite a lot of times during the course of a fight. 

SM: Groves went on to win a world title. But there are fighters like Meldrick Taylor or more recently Michael Conlan who suffered dramatic late knockouts and their careers never really recovered. There's still time for Conlan but he's lost two fights since being knocked out by Leigh Wood. 

AC: One thing I didn't do was speak to someone who had never been the same fighter again after getting knocked out. Those fighters are few and further between than people might think. With Michael, I made a tentative inquiry via his brother Jamie. We had a good chat but he gently said to me, 'I don't think he's going to want to do that.' 

I spoke to Anthony Yarde and Fabio Wardley. But if I'd asked all of the other guys about their experiences when they were active fighters, I wouldn't have got anything like the same answers. They can't be that honest - admitting to fears and fragilities and nerves when you're fighting. 

SM: Did you have a hitlist of fighters you wanted to speak to? 

AC: I'd been thinking for a long time about who I would need to cover everything I wanted to cover, which was the two sides of the knockout. What's it feel like to knock somebody out? What's it feel like to get knocked out? And what does it feel like to take a fight where everybody thinks you're going to get knocked out - such as Tony Bellew against David Haye or Amir Khan against Canelo Alvarez. 

I thought to myself, if I can get Froch, Bellew, David Haye because he was a knockout merchant, Amir Khan, Ricky Hatton, Matt Macklin and Jamie Moore because theirs is the classic, type-two, deep in the fight knockout - if I can get all of them, it won't really matter if I don't get anyone else. Luckily I did get all of them. 

It was amazing how willing people were to talk. Ricky Hatton has talked about it a lot, but you're still revisiting something that can't be his favourite topic of conversation. Amir was amazing. Initially he went into a slight autopilot - 'I got knocked out, it was my first knockout.' I said, 'No, I mean in the ring at that moment, what do you remember?' And he went 'Wow, OK!', and he gave me a brilliant answer. I've got the feeling that no one had asked him that before. 

SM: No. Probably for obvious reasons. 

AC: But they don't see it as being shameful. There's that old phrase: 'If you walk in the rain, you're going to get wet.' For them it's: 'If you box for long enough, you're going to get knocked out.'

Froch says the same thing. "Just because it didn't happen to me doesn't mean that I didn't think it could. I knew it could have happened to me. It just didn't." 

I spoke to a doctor about this, Neil Scott [medical advisor to the British boxing board of control]. The physiology of people is different; some people are more difficult to knock out than others and he doesn't really know why that is. They've all trained really hard. What decides whether somebody does or doesn't get knocked out? It is something we can never really know.

SM: There's a fascinating Teddy Atlas observation in the book about how getting knocked out is a form of submission. 

AC: Outside of type-one, yeah. He argues that your innate mental ability to refuse it diminishes once it's happened to you once. Your will to survive it drops and there's not much you can do about that. 

SM: I also loved the Muhammad Ali quote - being hurt in the ring and seeing the Near Room. "A door swung open and inside he could see neon, orange and green lights blinking, and bats blowing trumpets and alligators playing trombones..." 

AC: It's mad, isn't it? George Plimpton reproduces that quote in Shadow Box. I've heard so many stories from fighters about the mad stuff they've done after they've been hit really hard or knocked out. Froch got hit by Jean Pascal hard in the eighth round and then doesn't remember anything until he's back in the changing room. They'll be able to fight on even though they're in that state; fight for round upon round upon round, which they'll never remember. 

SM: Footballers must be subbed off with concussion; boxers are expected to continue getting punched in the head. 

AC: Ngannou vs Joshua is an interesting one. He got knocked down in the second round and you could tell that he was bang in trouble at that point. The referee could have stopped it but Ngannou would never have wanted that fight stopped. He would've preferred what happened to him than getting stopped on his feet. 

Guys at that level, they do need to be saved from themselves at times. Given the choice, would you rather sit on your stool and get your trainer to pull you out or would you rather walk straight back into the fire and get knocked out? They will choose the latter every day of the week. It seems insane to us but that's how they are.

SM: I waited hours for Joshua-Ngannou and the fight barely lasted five minutes.  

AC: But you're not dissatisfied. 

SM: The opposite. You're thrilled. It's the power of the knockout.

AC: Exactly. In the 1980s, nobody went to a Mike Tyson fight and felt short-changed - even though you're paying however much for a ticket and it ends after 90 seconds. 

SM: You're going to watch Tyson - you feel short-changed if it lasts longer than 90 seconds. The mentality of the fighters is fascinating but so is the mentality of the audience. Fighters are often compared to the gladiators of ancient Rome. It's a fair comparison in many ways, but equally the crowd at a fight isn't that different from the crowd of the Colosseum, baying for blood.  

AC: No, it's not that different but that's OK. It is this natural instinct that people have and that's why, despite everything, I think boxing will endure. I don't think it will really change that much. I mean, it has changed quite a lot down the decades... 

SM: I looked up the boxer with the most knockouts in history. A British fighter called Billy Bird with 138.  

AC: Fights were much more brutal and went on far longer. Now they will get stopped much more quickly. Maybe things will continue to go a little bit further that way but I don't think that people will try to have fights without the knockout. 

SM: No one would watch. Even now, fighters without knockout power normally struggle to sell tickets. It's interesting, you note in the book that the closest thing to the knockout in non-combat sports was the golden goal in football - and that got scrapped for being too abrupt. 

AC: You want to make things as relatable as you can. On the face of it, boxing's not very relatable and the knockout isn't very relatable. In other sports, the golden goal is the one thing that I could think of where it's all over when it happens. There might be more time left on the clock but it's over.  

SM: Checkmate in chess? Although any high-level chess match, the player knows the mate is coming - so it's a type two knockout. But you can still get sudden checkmates in lower level or timed matches. One bad move and you're done.

AC: No, that's right. That's a knockout. You make a mistake, your concentration levels slip for a second... 

SM: And their castle's on your back rank. 

AC: Golden goal was the only thing that came to me. On the surface, it was a great idea. It sounds amazing, but people didn't like it because it didn't seem fair. It just didn't seem fair that it could just be over like that. Every other sport, the score has to be incredibly close for any type of last-minute or sudden-death decisive moment. Whereas in boxing, you can be losing quite comfortably and then bang - it's done. 

SM: In the book, David Haye talks about his corner waving off the first Bellew fight. He's literally fighting on one leg and still thinks he could be about to unleash a winning uppercut.   

AC: In his head he could still win. Haye was great. I pretty much reproduced what he said verbatim - he told me exactly what I wanted to know. He explains that idea of going out on your shield or being prepared to die really well.

For people, it does seem irresponsible, doesn't it? You can decide that you're prepared to die but as Haye says, it's not like that. It's not like someone warns you between rounds: 'If you get hit with two more clean punches, you're going to get killed' and then you get to make that decision. That mentality is just about being prepared to push it and push it and never stop pushing it.

In boxing, we know what that can mean, but it's not like you get the heads up. If you want to be a winner at the top level, that is how you have to be.

Deontay Wilder vs Tyson Fury

SM: Is there anything that surprised you when writing the book? 

AC: I was surprised by how willing people were to talk about getting knocked out. I never thought they wouldn't talk about it but I was surprised how fine they were with getting right into the bones of it. People were enthusiastic to talk about it. 

They don't see it as anything to be ashamed of. I wouldn't go as far as to say that they see it as a badge of honour but in a way I think some of them do. Because they know they could have taken a knee or sat on their stool or whispered in their trainer's ear. They could have done all manner of things but they didn't. 

Of course they didn't want it to happen. Nobody wants to get knocked out. But if you box for long enough, you'll find yourself in a situation where you will get faced with a choice: either you do knowingly submit or you don't and you get knocked out or saved by the referee or your trainer. And they all are convinced that they will never choose the easier option. But none of them ever know that until they're in that situation.

It's a relief for them if they find themselves in that situation and it turns out they are the man they think they are. Matt Macklin told me, when all is said and done, you want to be able to look in the mirror and see the man you think you are.

SM: That's a great line. Lastly, is there anything you feel that you learned when writing this book? 

AC: I already suspected this, but I learned that boxing, extreme as it is, the situations that they all go through and they have to deal with mentally, is a lot more similar to everyday, 'real' life than people think. Because a big thing about it is realism and acceptance and how it is much, much better to live your life accepting what could happen to you - good and bad - than it is to bury your head in the sand and think that the bad can't happen. 

They all said the same thing: if you have a fighter who thinks that he's bulletproof and can't get knocked out, that is a disaster waiting to happen. You have to accept the fact that bad stuff can happen. That's something that translates to absolutely anything - because if you accept something bad might happen, you are more equipped to deal with it when it does.  

It's easy to look at fighters and feel like they would've been born invincible with unshakable self confidence, king of the school playground and all the rest of it. But they're not like that. They're just as vulnerable as anybody else and they choose to go into an environment where vulnerabilities get exposed in a way that they don't in others. 

It's compartmentalisation. You need to accept that you could get knocked out because that fear of it happening is what will drive you to do everything you can to make sure it doesn't. But on the night, you need to flick this switch whereby you decide that this thing that you accept could happen is definitely not going to happen. 

If you think about it, we all have to do that in different ways. Take a job interview: - you need to go into it believing that you're definitely going to the job while also accepting that you're probably not going to be successful.

We are a lot more resilient than maybe sometimes we think we are. What might seem like the worst possible thing can happen but you will find a way past it. You will. You don't lose a fight by getting knocked down. You lose a fight if you don't get up. And that's really what it's about. 

There's no getting up from some knockouts in the moment - like Teddy Atlas says, for that moment the lights are switched off and there's no turning them back on. But the key phrase is 'in that moment' - because you've got to turn them back on at some point. 

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You can purchase The Knockout here