The gun used to shoot John Lennon was still smoking when Frank Warren promoted his first licensed boxing show, at the Bloomsbury Crest Hotel in central London back in December 1980. And in November it will be 20 years since another gun was turned on Warren himself, by a mystery assailant, the former world light-welterweight champion Terry Marsh having been cleared of attempted murder. But then scarcely a year goes by in Warren's tumultuous life without this anniversary, that milestone, some worthy of celebration and some not.
Meanwhile, the show goes on, literally so in the case of Warren's new protégés, the young Olympians James DeGale, Frankie Gavin and Billy Joe Saunders. In Birmingham on 28 February, Warren's 57th birthday, they all make their professional debuts, the start of what their backer believes could, should, be the road to global fame and fabulous fortune.
"If James DeGale ends up winning the world title he will be the first [British] Olympic gold medallist to do so, at least in my memory," Warren says. "If he stays focused he can do it. Frankie Gavin the same. He's a bit of a playboy but a great little fighter. And Billy Joe's a natural, a Romany kid, and none of them have ever won world titles. We'll see whether he's got the discipline, because you can get by on talent but only so far. Hard work and dedication get you over the line."
Nobody ever accused Warren of a lack of dedication, or a lack of judgement. Rarely does he overestimate a boxer, which is where dozens of other managers and promoters have slipped up down the years. It was a surprise, therefore, to hear him suggesting in December that he could yet guide Audley Harrison to a world title, having for years been one of the big man's most outspoken critics. But the rapprochement didn't survive Harrison's latest dispiriting defeat, to the Irish journeyman Martin Rogan.
"I've let him go. We spoke after he got knocked out by Michael Sprott on one of my shows and he felt he still had it in him. I decided I would try to get it going. It didn't work. Audley's career's been like Pop Idol in reverse. A blaze of glory fizzling out to nothing. His problem is that he's not got the devil in him."
Which, as we sit back in the grand atrium of London's Landmark Hotel, begs a question. Is the devil still in Warren himself, now that he is wealthy beyond any dreams he could have entertained as a teenager taking home, to the family's council flat in Islington, the £8 weekly pay packet he earned as a trainee solicitor's clerk with J Tickle & Co on Southampton Row?
He smiles. "There are times I think 'screw this, it's a pain in the arse'. I get fed up with some of the people I deal with. But if you don't get disappointments in life, you don't appreciate the good things."
It is an admirable philosophy, but there is still a disappointment he wants to get off his chest, in the form of Joe Calzaghe, who split abruptly from Warren claiming that he was owed money. It is the Noble Art's perennial lament. And while Warren holds no great warmth towards Mickey Duff, one of the cartel of promoters who didn't exactly welcome him on to the scene with open arms all those years ago, he is fond of quoting what Duff once said about relationships in boxing: if you want loyalty, get a dog.
"The Calzaghe thing was the biggest disappointment I've ever had," he says, as softly spoken as ever but now leaning forward, eyes shining. "Total disloyalty."
The words hang in the air, while I dare to suggest that the now retired champ seems like a bright and decent fellow. "In some ways he is, but he's also small-minded, with a little bit of that green eye. He used to moan years ago that he didn't get the same publicity as Ricky Hatton and Prince Naseem. Well, Ricky went out and promoted himself. He got off his arse, doing after-dinner speaking and all that, though the downside of that was that he became a boozer. And Naz captured a whole generation of young boxing fans. I did deals with TV for Joe on the back of him. I said, 'We've got Naz, we've got [Frank] Bruno, and we've got Calzaghe ... if you want them you've got to take him as well'. That's how we got him going."
As for Naseem and Hatton, they too eventually divorced themselves from Warren. If he'd bought loyalty every time he lost a fighter, his Hertfordshire mansion would look like Battersea Dogs' Home.
"Well," he says, "with Ricky I expected it deep down. There wasn't huge closeness there. But I did a good job with him. He'd banked seven million quid even before he beat Kosta Tszyu, so if Kosta had beaten him he'd have been set up. That's my philosophy. Get 'em to the stage where they're OK even if it goes tits up." A heavy sigh. "Calzaghe banked £18m with me, and sure, I made money too. That's the business I'm in. If I don't make money they're not going to make money. On his own he did some stupid deals. The 50-50 deal with [Bernard] Hopkins was ridiculous, and not learning from it, doing another 50-50 with [Roy] Jones..."
Warren shakes his head at what might have been. "It's like Arsenal signing Arshavin. It all went to the wire because everyone was playing their cards. Whatever sport you're in, you go in to negotiate with your best cards. But Roy Jones couldn't get arrested before the Calzaghe fight. Why give him half the promotion? Crazy."
I ask him whether he has seen Calzaghe since. "I've had one meeting with him, at a hotel in Paddington. It got very heated. His father never wanted it [the split], you know. He kept sending me texts saying I was the best fella in the world. Of course, I appreciated his position. Blood's thicker than water. But like I said to him, if my kids do something wrong, I'm there for them, I'll love and support them, but I will also tell them that they've done wrong."
Needless to add, Warren is well aware that one, two or all three of the young boxers he has fighting in Birmingham later this month might, somewhere down the line, do a Calzaghe. For boxing people, there are almost as many occupational hazards outside the ring as there are inside. But while they are with him, they will get the benefit of decades of astute matchmaking in a sport that Warren believes is healthier than ever. "People talk about the good old days but even Wembley back then only held 10,000. We do shows now where we get 20,000, in the O2 Arena or up at the MEN."
And what about the astute matchmaking? What does he consider to have been his greatest triumphs?
"Oh, sending Danny Williams over and seeing him knock out [Mike] Tyson, that was a good bit of matchmaking. Calzaghe beating [Jeff] Lacy, Hatton beating Tszyu. The knockout punch is about perfect timing, and so is matchmaking, picking the right guy at the right time. I think I've been good at it. I've managed more British, European and world champions than anyone. But you never know. At the moment I've got Amir Khan fighting [Marco Antonio] Barrera, and I'm hoping I've got it right but I might not have. It's a responsibility, looking after somebody's kid. That's why I like to meet the parents. The other week I met [Tony] Jeffries, the kid from Sunderland. I made him my offer and his dad wanted to take it, but the lad said he'd been offered huge money elsewhere. I said, 'Great, but it's undeliverable.' He said, 'Well, I'm going with it.' Sure enough, the guy couldn't deliver. So Jeffries came back to me and asked for the deal I'd offered. I said, 'I'm sorry, that bus has gone, I've spent the money elsewhere.' And that was that. A great shame, really."
Warren smiles. He should worry. At almost 57 he has his health [despite losing half a lung on the operating table following the shooting], his hair [immaculately blow-dried], his fortune and all his old muckers from boyhood. "Yeah, we still meet once a month, seven or eight of us. One's a cab driver, another's an architect, there are a couple of rascals. We turn back the clock and have a laugh."
They must all laugh their socks off at his story of the one that got away, one that has nothing to do with boxing. "A pal of mine, Jay Larkin, rang one day while the Don King case was going on [Warren sued King, unsuccessfully, over a contractual dispute]. He invited me to meet this girl who had a musical she wanted to put on, and was looking for investors. We met at Langan's, had a nice lunch, and she told me about it. I said, 'I'm in, I'll put the money up next week.' But then the judge froze all my assets." A pause, perfectly timed. "The show was Mamma Mia. It's made billions." Has he been to see it? "You're joking." He grins. "That's how I met my Waterloo."
The Olympic gold medal winner James DeGale, and fellow Olympians Frankie Gavin and Billy Joe Saunders, make their professional boxing debuts at the NIA in Birmingham on 28 February. For tickets, call 0844 338 8000 or visit www.theticketfactory.co.uk