Preamble: Morning. It's a pity Roy Jones Jr couldn't shave a few years off for this fight – well actually, 15 years to be honest. He reminds me of Oasis, full of bluster in 2008, but with his biggest hits belonging way back in the mid-1990s. But when Roy Jones Jr was good, he was unstoppable. The punch that floored the undefeated IBF super-middleweight champion James 'Lights Out' Toney at the beginning of the third round in 1994 was like a bolt from the blue. It also announced him onto the world scene. And if anybody still needed convincing of his class, four months later, he knocked out Antoine Byrd in the first round with rare skill and raw power to defend the title.

Despite a disqualification defeat to Montell Griffin in 1997, Jones Jr dominated at both super-middleweight and then light-heavyweight through the late 1990s until his fading star burnt out with three defeats in a row in 2004-05 – two to Antonio Carver and one to Glen Johnson. These defeats, two knockouts and a points loss, effectively put an end to his reputation as a serious prospect. Now aged 39, and lacking the incredible speed in the ring that used to be his trademark, Jones Jr will have to draw on all his experience and ring craft to score a victory against Calzaghe. At the weigh-in he looked enormous, so perhaps he's hoping to conserve his energy and, like Bernard Hopkins displayed with some success, attack the Welshman sparingly, but with great power.

As for the unbeaten Joe Calzaghe, he has maintained a high level throughout his career. People first stood up and took note of his talent 11 years ago when he beat a below-par, but still dangerous, Chris Eubank over 12 rounds. He has grown into himself as a boxer in the years since, recovering from his first ever knockdown against big-hitting Byron Mitchell in 2003, to annihilate his opponent with a deadly assault of 26 unanswered punches to claim victory just a little over a minute after tasting the canvas himself.

If the bout with Mitchell was evidence of Calzaghe's burning pride, his clash with Kenya's Evans Ashira in 2005, proved he had the heart and skill worthy of an undefeated champion. After breaking his left hand early in the third round, Calzaghe fought on for nine rounds with only his rapid right jab to win a unanimous points victory. This rare ability to fling out countless jabs, thus giving his opponents no let-up, has served him well over the years and came to the fore in career-defining points wins against the heavily fancied Jeff Lacy and the hard-as-nails Dane Mikkel Kessler, whom Calzaghe defeated to unify the WBA, WBO and WBC super-middleweight titles.

Calzaghe's biggest weakness could be a feeling within himself that he should have perhaps hung up his gloves after his brilliant win against Kessler. At light-heavyweight against the aged but crafty Hopkins, Calzaghe looked like he was winding down as he struggled to get inside the American. Thanks to a desperate flurry of punches late in the fight he won narrowly, and some would say fortuitously, on a split decision. I can't see that he will show any such complacency in his final ever fight this morning, but there is just enough doubt lingering around Calzaghe's brittle hands for me to believe that he'll have to go the full 12 rounds to end his career with a perfect record.

Right, I'm back and fully loaded on coffee. In the pre-fight build-up Calzaghe has already intimated that he might continue fighting after tonight. "This is probably my last fight," he said, much to the chagrin of his concermned mother I presume.

Here are some of your pre-fight emails: "This reminds me a lot of the Lewis vs Tyson fight," says Chay in Chorleywood. "A good British boxer who's not really had many decent opponents to face during their prime, and wants to be seen to beat a big name who was once one of boxing's best ever. And just like Lewis, Calzaghe will systematically take Jones apart until he can't take anymore. Maybe 6-8 rounds." Jeff Lacy was no mug Chay and Kessler gave Calzaghe one hell of a fight, but I agree that Calzaghe never got involved with the big names like Roy Jones Jr and Bernard Hopkins when they were at their best, and I doubt he'd have been up to their level in the mid to late 90s.

"I'm Welsh and living in Los Angeles," says Michael Aston. My brother lives in LA Michael, say hello if you see him. He's got dark hair and - oh never mind... Continue. "I want Roy to win this one. He is a most noble man and a truly great champion. The Italian/Welsh boy will have the greatest lesson there is: humility and respect." Interesting Michael. Doesn't Jones Jr cross the border to go dog-fighting in Mexico? Not much nobility in that. But anyway, an interesting switch of allegiances. I'm not sure Tom Jones would be too thrilled with you backing Jones Jr though.

The Observer's Kevin Mitchell is at ringside and here is his scene-setter:

All week, the word has been that the Garden would be half-full for this fight - but, whether or not the gate was papered over by complimentaries, it isn't a bad turn-out. And most of the singing, of course, has a Welsh lilt.

The bars around the famous old barn have been heaving for hours. Calzaghe has been a 3-1 on betting favourite with most odds-makers, Jones a 3-1 outsider. However, early 50-1 odds on a draw have been cut to 20-1 now punters have seen the value there.

So far there has been nothing on the undercard that you would remember for long, apart, maybe, from the performance of Emanuel Augustus, who is 33 and has been boxing since 1994. He hip-hopped, he shimmied and he banged as best he could, smiling all the time at his considerably younger opponent, Francisco Figueroa. None of which prevented his posting the 30th defeat of his 72-fight career. They never give it to the old guy if it's close.

The celeb count isn't extraordinary, although Lennox Lewis got a good cheer as he strolled to his seat. Mikkel Kessler, who gave Joe his toughest fight, is at ringside, as is Bernard Hopkins, still angling for a rematch with whoever wins the main event. That won't happen.

More emails: "Is this an exhibition match?" barks Derek Talbot. "We have one of the best pound-for-pound fighters ever reducing himself at 39 to fighting a slap/box boxer who always chooses the easy fight. Big deal if Calzaghe wins. He's won no respect regardless." It does have that Harlem Globetrotters feel in which names are used to sell meaningless contests. Let's hope Jones Jr has something left in the tank to make this mean something.

"Hopkins is sticking by his prediction of a win for Jones Jr," says Kevin Mitchell, ringside in New York. As Calzaghe's last opponent I suppose Bernard Hopkins knows better than most how to give the Welshman a rough time, but surely a Jones win is a tall order.

The final fight on the undercard is still ongoing so we've a while longer to wait before the main event gets underway. Meanwhile your predictions keep coming.

"Jones before round eight is a worry," says Laurance Langdon. "But Joe over the 12, thanks to his sheer work ethic."

"Having hopefully sneaked the fight on some illicit broadband network I'm determined to stay awake," says tinternet criminal Paul Woods. "I think Jones will knock Calzaghe down in the first couple of rounds but fancy Calzaghe to win the bout, assuming he gets back up again. I expect Jones to unload a few bombs from the outset and 'check the chin' of Calzaghe. Calzaghe also has an unhealthy prediliction for standing toe to toe against stronger opponents which could find him out. I won some money on Samuel Eto'o earlier and it's all going on a Calzaghe knock down, and Calzaghe on points." Illegal Internet sites, gambling, and staying up late? You live life on the edge Mr Woods.

"Almost all boxers go on too long (some twice or thrice) - isn't this a fight to decide which is guilty of this inevitable hubris?" says Gary Naylor. "Because on that reasoning, Calzaghe should cruise it." All boxers are spurred on by pride and I can't blame somebody like Jones Jr wanting to restore some of his by taking on an undefeated fighter. It reminds me somewhat of a gambler who is losing heavily and tries desperately to win back his stake by going for broke. If he loses, his reputation lies ever more in tatters, if he wins, well he's either back in the game, or he can retire content.

4.22am: The final fight before the main event plods on. It's in round nine so hopefully not too long to go. Jones Jr had a bunch of cronies whoopin' an' a hollerin' as he shadow boxed in preparation in his dressing room. Calzaghe looked ultra-relaxed. In fact, he looked a little too at ease - he ought to get pysched just a wee bit in my opinion.

Meanwhile, back in my inbox: "I'm stuck in Bangkok with no access to a TV with the fight on it," laments Ronn McMillan. "I recall watching Jones Jr's finest/unfinest hour, when at the Seoul Olympics in 1988 he won his final easily, then had the gold medal handed to his Korean opponent. The Koreans were never too subtle when it came to cheating. I rate Calzaghe though, and want tonight to be his night. Go for it Joe." I might just add that it was Ron McMillan who intimated Koreans are fond of cheating, not me.

We're just about ready to rumble! But while the razmattazz builds up here's Laurance Langdon with career advice for Jones Jr and Calzaghe. "Both of these guys are finishing on this fight, no matter what Jones may say. If Jones wins, his claim for the best of all time is cemented, if Calzaghe wins he can go out saying he beat them all, despite some being past their prime. It's a legacy fight, and a massive pay day to boot. It's freezing in Atyrau [Kazakhstan], so we need some excitement to warm us up."

Build-up: Jones Jr enters the ring wearing an orange hoody and looking particularly moody. He's greeted by a mixture of boos from the travelling Welsh support and cheers from the home crowd.

Calzaghe looks cock-sure in a ridiculous sequin vest. Not the best choice of attire for what is probably your final fight. Not that it matters if he wipes the floor with Jones Jr.

The national anthems are blasted out into Madison Square Garden. The ginger American woman wins the sing-off in my opinion. She empties her lungs with much more vigour than did the Welsh singer. Maybe that's an omen.

The orange tanned PA gives it his all as he presents the fighters. It takes him about five minutes to list all of Jones Jr's achievements. Calzaghe grins as he is presented as undefeated. He punches the air and we're ready to RUMBLE!

Ding ding! Round one: Calzaghe throws out his jab very early on and pins Jones Jr against the ropes and works at his body. Jones appears to weigh up his opponent and throws a rapid left hook in the centre of the ring. It doesn't connect but it acts as a warning. They both trade punches in the corner. Calzaghe works a neat combination into Jones' body... then Calzaghe goes down! Amazing! After a quiet start Jones lands an straight left to floor Calzaghe in much the same way Hopkins did with his right in the first round. Calzaghe gets up gingerly and throws out some wild punches and manages to survive. What a start!

My score: Calzaghe 8-10 Jones Jr

Round two: Calzaghe is the aggressor early in this round. Jones sucks it all up and waits like a coiled cobra to attack. The Welshman doesn't allow him too though as he throws Jones onto the ropes and follows up with a flurry of punches to score points with the judges. Jones sticks out his tongue as if to say 'you didn't hurt me' but in my book Calzaghe won that round. This fight has been anything but a meaningless exhibition - in large part thanks to Jones, who looks much more youthful than 39.

My score: Calzaghe 10-9 Jones Jr

Round three: Calzaghe flies out with intent and looks more spritely on his feet than he has in any other round. He pins Jones back into the corner and works Jones's body before landing a big right hand over the top. He grins as he dances into the centre of the ring and goes toe-to-toe with Jones, who has nothing in reply. This is much better from the Newbridge southpaw. He must have landed four times as many punches as Jones in this round and many have connected too. Calzaghe struts on the bell and wiggles his hips at his opponent who doesn't like that one bit. The bell goes and Calzaghe will regret showboating if he is dumped on his behind again.

My score: Calzaghe 10-9 Jones Jr

Round four: This fight is echoing the Hopkins battle. Calzaghe is playing catch-up. Jones doesn't have the water-tight guard of Hopkins though and I expect him to have to take a few more on the chin than Hopkins did. Calzaghe ought to be careful not to pose too much though as one rapier-like punch from Jones will floor him. Jones does catch Calzaghe with two clean jabs towards the end of the round, but the Welshman laughs them off just before the bell calls time. Calzaghe's work rate wins him the round though.

My score: Calzaghe 10-9 Jones Jr

Round five: Jones takes the pace out of the fight, by allowing Calzaghe to back him into the corner. Calzaghe characteristically lands a machine gun-like flurry of punches in the corner but Jones covers up well. Calzaghe steps up the pace and lands through Jones' guard and shakes the American. Right up to the bell the two of them trade punches. Calzaghe continues to land more blows but Jones always connects with the more accurate powerful shots.

My score: Calzaghe 10-9 Jones

Round six: "Slightly worrying how confident Joe is putting his unprotected face in Jones's all the time," says Alex Hughes. "He looks great though. Either another Lacy performance or he'll look very stupid flat on his back. Don't want to take the mickey too much with someone of Jones's calibre." Agreed Alex. Enzo Calzaghe reckons Jones will run out of steam. He may do but while he is standing he is a great threat. Calzaghe continues to put in the work to the body with his combinations. Jones invites Calzaghe onto him and then lands a terrific uppercut. Calzaghe responds well in the corner but Calzaghe's chin must be wobbling after that.

My score: Calzaghe 9-10 Jones Jr

Round seven: Jones Jr has already proved his doubters wrong with his performance so far. He looks like he has got a second wind and manages to stay up as Calzaghe lands a crushing left hand midway through the round which sends Jones crashing onto the ropes. Calzaghe pounces on the opportunity and lands a straight left hand which gouges a cut above Jones Jr's left eye. The American survives but he is left with blood all over his upper body. That was a great round for Calzaghe.

My score: Calzaghe 10-9 Jones Jr

Round eight: "Joe leading comfortably after six rounds," says the Observer's Kevin Mitchell at ringside. "Five rounds to one, through sheer volume of punches, after coming through a nasty first-round knockdown, which he dropped 10-8. Pace relentless. Calzaghe super confident and Jones bemused by the number and quality of Joe's combinations." That's the ringside view. Meanwhile Jones has been shaken by that cut. He looks a mess with blood gushing from his eye. Calzaghe is like a predator playing with his injured prey. Jones can't see and Calzaghe continues to pound him with a relentless stream of shots. Jones bats him off with an uppercut but Calzaghe forces Jones to cling on until the bell. The doctor has got much work to do to clean Jones's cut up so he can continue.

My score: Calzaghe 10-9 Jones Jr

Round nine: There's a delay as Jones has his cut worked on. A replay from the last round shows a left hand from Calzaghe tearing across the cut. It's enough to make me wince never mind Jones. The American dances around and manages to limit the damage in the early exchanges in this round. Calzaghe seems content to hold off and wait for an opportunity to connect. He goads Jones - somewhat disrespectfully I feel - by sticking his chin out at his wounded opponent, who thankfully gives Calzaghe a jab to the mush. Calzaghe has it on points now and only has to see this one home. Jones has to do something special through one eye.

My score: Calzaghe 10-9 Jones Jr

Round 10: Mercifully for Jones, the pace has dropped. He clings onto Calzaghe, who backs off and lands some crunching blows to Jones's ribs. The American legend is showing tremendous bottle. The whole left hand side of his face is crimson with blood. The fight should be stopped in my opinion. Jones survives another round. Calzaghe could be more ruthless and finish this but perhaps he's trying to lengthen his career.

My score: Calzaghe 10-9 Jones Jr

Round 11: There's another delay as Jones has a lot of first aid work on his eye. Calzaghe immediately homes in on the cut with his right hand, but Jones Jr connects with a single accurate left. Calzaghe lands a solid right jab which Jones bizarrely acknowledges by saying "good shot Joe." Calzaghe showboats again and... again gets his just deserts as Jones swings a right hook his way and connects. I'll score the round as a draw for Jones's sheer bravery.

My score: Calzaghe 10-10 Jones Jr

Round 12: There's a standing ovation as these two legends of boxing, who may never fight again, touch gloves for the final round. It's been a gruelling fight and a great spectacle. Calzaghe crouches low and invites Jones onto him. With his trademark lunge Jones almost dizzies Calzaghe with a crashing right which just grazes his ear. Calzaghe skips on the spot to prove how much he has left in the tank, but in my opinion he should fuel a couple of punches and try to down Jones instead. Like a bloodied warrior Jones has one final lunge at Calzaghe which misses and as the bell sounds the two fighters embrace.

My score: Calzaghe 10-10 Jones Jr

My result: A quick tot up of my scores puts it at Calzaghe 117-113 Jones Jr

The judges' result: All three have it at Calzaghe 118-109 Jones Jr

Joe Calzaghe wins comfortably after a shaky start. For his sake it's a blessing that he has an iron chin because he needed it after being floored midway through the first round.

Post-fight musings: "I won't make my final decision yet," says Calzaghe when asked about his future. "I'll go home and think about it." I think that's a clue that Calzaghe will have one last 'last' fight. The PA suggests Chad Dawson. We'll have to wait and see who he will face if he does decide to continue boxing. After tonight's performance I hope he does. Thanks for all your emails.