Anthony Joshua retained his IBF, WBO and WBA after beating Kubrat Pulev.
The 31-year-old Briton was close to winning when he floored Pulev in the third round after a sweet right hand but the challenger recovered to test the home favourite in front of a limited crowd of 1,000.
Pulev, 39, remained dangerous, without causing Joshua many anxious moments, but there was no escape in the ninth.
Joshua landed a clubbing right upper-cut which sent Pulev to the canvas. The Bulgarian got back to his feet but Joshua connected with another huge right hand to end the contest.