Anthony Joshua survived a brave, doomed challenge from Dillian Whyte – as well as an equally ill-considered ring invasion by a posse of the Brixton fighter's fans at the end of the first round – to place himself firmly at the heart of the heavyweight division on Saturday night by winning the British title vacated by Tyson Fury.

They will meet eventually, the Olympic champion and the world title-holder, and what a prospect that is. If Fury is still champion after his rematch with Wladimir Klitschko, he will do well to survive the power of a fighter who has reached superstardom while just coming off the nursery slopes of his sport. He could not have won more impressively.

At one minutes 27 seconds of the seventh round, Joshua landed the sort of uppercut that would have decapitated a bull and which left Whyte in a motionless heap along the ropes near a neutral corner. As hard as Whyte tried – and he did have one-off successes here and there – his fate was sealed a lot earlier.

“Well, well, well,” Joshua said in the ring as he clutched the Lonsdale Belt, still one of the most treasured prizes in boxing. “So this is the British heavyweight title. I had the strength to knock him out and I found a way. I broke him down.”

Asked if Whyte had hurt him in one of his many wild flurries, he said: “It’s a fight, man, but I started to relax and broke him down. I learnt a lot about myself.”

Whyte not only entered the ring second, he brought with him a knot of hardcore supporters who could not be persuaded to leave the inner circle.

While the overwhelming majority of the 17,500 paying customers were with Joshua, these guys, yelling throughout in this reporter’s right ear, were solidly with their man.

At the end of a dramatic first round, in which Joshua systematicallly beat Whyte around the head with crunching blows from both hands, they invaded the ring to complain about a blow after the bell from the Watford fighter, and it nearly descended into an all-out brawl.

They left soon enough but the atmosphere was heated up a hundredfold. Whyte showed enormous courage to weather another storm in the second. Joshua knew he was in a fight in the third, although he continued to pepper his man with punches that have put previous opponents down and out.

Whyte stayed in the hitting zone, but was taking far more than he was landing. His legs wobbled on the end of repeated right crosses. Joshua was now having fun.

Whyte, a former kick-boxer, began to blow in the fifth as his elementary boxing grew increasingly ragged under pressure, while Joshua planted his feet and went methodically about his work.

At the start of the seventh, Whyte somehow stayed upright after a powerhouse right rocked his temple, but there was nothing he could do about the subsequent uppercut, possibly the punch of the year so far.

Whyte sat on the floor for fully a minute before the doctor allowed him to his feet and he did not appear to know where he was, or which particular truck had just run over him. If he could have fought on, he would have. As it happened, he did well to stand up.

Chris Eubank Jr should lose the appellation now. He looks like he could be every bit as good as his father – perhaps better – and earned a shot at Daniel Jacobs' WBA middleweight belt with by far the most impressive performance of his 21-fight career to stop the stubborn Irish puncher Gary "Spike" O'Sullivan after seven one-sided rounds.

O’Sullivan showed no respect for Eubank’s power in the first round, clowning with his hands behind his back, grinning and showboating, but what happened thereafter was an education for all of us.

The Irish smile evaporated in the second round on the end of a crunching uppercut, followed by an attack that went pretty much all the way to the bell. From there to the end – apart from brief parity in the third – O'Sullivan stayed on his feet but absorbed a quite brutal beating until his co-trainer Steve Collins pulled him out.

“That was most satisfying,” Junior said. Unlike his father, he does rock-solid understatement.

Tony Bellew, seven fights into his cruiserweight campaign after failing at light-heavy in his previous world title campaign, edged a tough 12-rounder against Mateusz Masternak to claim the vacant European title. Whether he can use it for a shot at another world championship two years after Adonis Stevenson stopped him at 175lb in six rounds is a hard call on this performance.

Masternak – no poet – fought with functional menace: predictable, committed and hurtful. He brought an ominous 67% stoppage rate over 39 bouts and tried his best with chopping rights behind a stiff jab to improve on that statistic.

Someone as smart as Bellew should have been able to not only avoid more of these mechanical onslaughts but fashion an effective counter plan, but he too often fought in bursts. However, a storming finish, in which he had the Pole out on his feet in the final round, was enough to give him two margins of 115-112 and a third of 115-113. He deserved it – just.

There do not appear to be many places for Kevin Mitchell to go at 31 after he suffered his fourth stoppage loss at elite level. Thirteen seconds from the end of round five, the formidable Venezuelan Ismael Barroso put the Londoner on the floor for the third and final time to win the WBA's interim lightweight title, notionally putting him in the way of Anthony Crolla, or perhaps Terry Flanagan.

Mitchell, off balance, went down in centre ring from a glancing blow in the fourth and was fresh enough still to finish the round strongly, but Barroso was getting the upper hand. Another right made more solid contact in the fifth and Mitchell went over again. He retreated to the ropes but there was no rest there for him and Barroso unloaded at will before decking the Londoner again.

Barroso, 32 but full of life, came with a frightening 17 of his 18 wins finishing early, and had been due to fight the Liverpudlian Derry Mathews for this belt in April; it is unlikely anyone will be chasing him with phone calls on Monday morning.

(Guardian service)