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.
Walkden predicting golden Olympic summer to unite the nation and recreate spirit of 2018 World Cup
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.
Taekwondo star Walkden backing Joyce's lion artwork to help her roar in Tokyo
Promoter Arum says fight between Fury and Joshua agreed