Wladimir Klitschko knocked out challenger Eddie Chambers in the 12th round to retain his WBO and IBF heavyweight titles in Germany.
The 33-year-old Ukrainian managed to secure his 48th knockout win in 57 contests with a left hook which sent his American opponent to the floor with just five seconds of the 12th round remaining.
Chambers, known as 'Fast Eddie', had only lost one fight from 36 going into the bout, but he was defensively-minded throughout as he was conceding five ins in height and 35 lbs in weight to Klitschko.
It looked like the dull encounter, in front of 51,000 spectators in Dusseldorf, would go to a points decision, until Klitschko finally produced his knockout blow.
Afterwards Klitschko said: "I don't think he ever really hit me, but it wasn't easy. I wanted to be too perfect maybe."
He added: "I have to give him credit, he was fast.
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He doesn't have much punching power and his game plan was gone by round six."