Cook was fighting at super-featherweight for the first time
England's Nicky Cook boxed superbly to beat Alex Arthur on points and strip the Scot of his WBO super-featherweight title at the MEN Arena in Manchester.
Defending his crown for the first time, 30-year-old Arthur was out-thought and out-punched from start to finish.
Cook, 28, landed a series of precise blows and fluid combinations to come through on a unanimous verdict.
Earlier, British heavyweight Audley Harrison claimed a 98-92 points victory over Brazilian George Arias.
Romford resident Cook was fighting at super-featherweight for the first time but looked in perfect shape and thoroughly deserved his win.
Arthur, previously the interim champion, was defending the full title he was handed after Joan Guzman moved up to lightweight for the first time.
He had weighed in at exactly nine stone, four pounds - half-a-pound heavier than Cook - and seemed to struggle to keep pace with the challenger's movement.
Cook's aggression and hand-speed proved too much for Athur and, but for a huge right hand landed by Arthur in the seventh round, the result was never in doubt.
"I'm absolutely ecstatic, you don't know how much this means to me and my family," said Cook.
"We had a great gameplan: 12 rounds non-stop, walk away with belt. But not flying round the ring, keeping an arm's distance - it worked and it worked a treat.
"We've worked extremely hard for 12 weeks and it's all paid off."
Harrison was booed by sections of the crowd en route to a 98-92 verdict, his second laboured victory of the year.
The 36-year-old former Olympic champion was rocked by a powerful right from Arias in the third of 10 rounds.
But the enigmatic Londoner did enough to claim his 23rd win professional win.
Afterwards, Harrison insisted he could still be world champion in 2009 despite his unconvincing display.
"Thank God for the victory. George is a tough durable guy, the crowd are always going to go with the underdog," he said.