Mark Chamberlain stuns Pierce O'Leary in IBO World title fight

By Tim Rickson2 Aug 2026 · 3 min read

Mark Chamberlain crowned new IBO World super-lightweight champion — Thunder rumbles in DublinQueensberry

Thunder rumbles in Dublin

Briton Mark "Thunder" Chamberlain (18-1-1, 1 KOs) stunned Ireland's unbeaten IBO World super-lightweight champion Pierce "Big Bang" O'Leary (19-0-1, 11 KOs) in front of his home fans, as he dropped him twice on the way to securing a 10th round knockout victory in Dublin.

The plucky puncher from Portsmouth had to climb off the canvas himself in the seventh round as the defending champ "Big Bang" O'Leary struck him with a rib-breaking body shot.

But just as momentum appeared to be swinging back in the favour of O'Leary, courageously clawing his way back into the contest, Chamberlain found a breakthrough and managed to get the stoppage late on.

He now moves to 18 wins with one defeat, bouncing back to winning ways for the first time since losing to Josh Padley in 2024. Prior to this bout, the 27-year-old Brit had only one won from his last three.

This biggest win of his career was Chamberlain's first fight since he drew with Jack Rafferty one year ago in Altrincham.

"First of all respect to Pierce for giving me this opportunity," the new champ Chamberlain told DAZN after the fight.

"I'm not a stranger to an away day and anyone that knows me knows that I will fight anyone and if that means that I have to go into the champions' back garden then I will do that.

"I've never been hurt before in a fight but that body shot stopped me in my tracks but fortunately I was able to get through it and weather the storm.

"We've been working on new things in the gym and it's all paid off, I asked Frank (Warren) in the dressing room before the fight if we could bring a show down to Portsmouth, I'd love that. "

After a cagey first round, challenger Chamberlain stunned the sold-out crowd of around 7,000 as he landed a flush left hand on local lad O'Leary, sending him flying back onto the canvas for the first time in his pro career.

Chamberlain then found another big shot in the next round as he ordered his opponent to the floor again with a short left hook.

But the champion O'Leary responded well to the knockdowns, rallied by his home crowd as he pressed on to find a way back into the fight.

He then found a breakthrough at the end of the seventh round as he backed Chamberlain into a corner and sent a punishing shot into his chest.

Chamberlain was slow to get to his feet but survived the count and managed to avoid major punishment before the bell sounded.

O'Leary continued to press on, with Chamberlain looking tired and the Irishman buoyed by the crowd.

But Chamberlain struck in the 10th with a combination that saw O'Leary drop his hands and then pressed on, landing a number of clean shots that included a straight right hand to send O'Leary tumbling into the ropes and to the canvas.

Fight promoter Frank Warren revealed after the fight that there is a rematch clause in the fight contract that could see the pair fight again in the near future.

Royston Barney-Smith decisions Reece Bellotti

"Sugar Boy Roy" outclasses "Bomber" Bellotti

British and Commonwealth super-featherweight champion Royston Barney-Smith (17-0, 8 KOs) beat fellow Briton Reece Bellotti (20-8, 15 KOs) earlier on in the night.

The 22-year-old from Southampton outclassed the experienced operator Bellotti across 10 rounds to pick up the vacant IBO intercontinental belt.

Former British beltholder Bellotti took the fight to the youngster Barney-Smith, stalking the southpaw and finding success as he pushed him back against the ropes and unloaded with dangerously intentioned shots.

But top prospect Barney-Smith boxed smartly off the back foot, picking "Bomber" Bellotti apart with a variety of punches and manoeuvring away from a number of aggressive surges with some his fast footwork.

The victory over the 35-year-old from Watford takes RBS to 17 wins without defeat since turning professional in 2022.