• A frustrated Okolie was twice docked points for holding and grappling as he lost his unbeaten record.
• Okolie suffered a first career defeat in his 20th professional outing.
Image: /BBC
Chris Billam-Smith became the new WBO cruiserweight champion as he dethroned former gym-mate Lawrence Okolie on a memorable night in Bournemouth.
Fighting in his hometown in front of 15,000 jubilant fans, underdog Billam-Smith floored Okolie three times en route to a majority points victory.
A frustrated Okolie was twice docked points for holding and grappling as he lost his unbeaten record.
The judges' scorecards read 112-112, 116-107 and 115-108.
Okolie - who was part of trainer Shane McGuigan's gym before the pair split earlier this year - suffered a first career defeat in his 20th professional outing.
"I love being a winner, I love being a champion but I have to take my hat off to him, it was very good work," the beaten fighter told Sky Sports.
"I am just pleased to be here in front of 15,000 with Chris, my friend.
"I just tried to keep my composure but those things do play on your mind. I trained really hard because I know what Chris is made of. He is made of the good stuff."
Billam Smith, a British, Commonwealth and European champion, won his maiden world title as he extended his record to 18 wins and one loss.
"I was sick in bed all week, I didn't eat from Tuesday to Thursday, I managed to put on a brave face," he said.
"I just want to dedicate this to my mum who has breast cancer at the minute. Mum, this is for you, I love you so much."
Billam-Smith shines as Okolie frustrates
On a clear summer's evening at the Vitality Stadium, and with the full-throated support of his Bournemouth faithful, 31-year-old Billam-Smith catapulted himself into boxing stardom.
The atmosphere was that of a football crowd but also remarkably intimate for a stadium fight. The sound of jeers for Okolie, cheers for Billam-Smith and chants mocking football rivals Southampton bounced between the four stands.
Okolie was under pressure to deliver an entertaining fight, having been criticised in the past for his awkward and far from fan-friendly style, often grappling his way to victory.
But there were two clinches within the first 30 seconds from Okolie, a sign of things to come.
The referee repeatedly separated the fighters each time Billam-Smith closed the distance. The challenger had a frustrated look on his face as early as the second, with Okolie given warnings for pushing and holding.
There were question marks about whether Okolie would revert to type or if trainer SugarHill Steward could transform the champion into a more entertaining fighter.
But Okolie would follow his single shots with more grappling, often bordering on wrestling.
Having sparred over 300 rounds together, Billiam-Smith presumably knows Okolie's strengths and weaknesses better than any other cruiserweight.
Out of nowhere, he unleashed a left hook which floored a reckless Okolie - who had never been down as a professional - in the fourth round. The Londoner got back to his feet but his legs were unsteady.
Okolie was docked a point in the fifth and seventh rounds, with referee Marcus McDonnell shrugging his shoulders to suggest he had no other choice.
The Hackney fighter fell to the canvas again in the 10th, leaning into a Billam-Smith left hook.
A bloodied Billam-Smith withstood a flurry in the 11th to once again drop Okolie with a punch on the inside before seeing out the win.
The night belongs to Billam-Smith
In an age in which an undefeated record often dictates a fighter's worth and marketability, Okolie must regroup after his shock defeat.
Okolie says he will activate his rematch clause. At 6ft 5in, he is a big cruiserweight and has also previously said he plans to move up to heavyweight in the future.
The night, however, belonged to Billam-Smith, although credit must also go to McGuigan for devising the perfect gameplan.
Billam-Smith first walked into McGuigan's gym as a sparring partner for George Groves and David Haye. Despite no decorated amateur career, he convinced the trainer to let him join the stable and has now reached heights few predicted he ever would.
For years he played second fiddle to Okolie. It was the Londoner who was picked for TeamGB and selected for the Olympics. Okolie was the man headlining cards and being pushed towards world-title fights when both were signed to Matchroom.
A British, Commonwealth, European and now world champion, Billam-Smith has shown he belongs at the top level on an evening that he, and the thousands in attendance on the south coast, will never forget.