Tshifhiwa Munyai ended Lee Haskins' bid to become a two-weight Commonwealth champion with a withering sixth-round stoppage in Bethnal Green.
The tall South African defended his bantamweight title and inflicted the first professional loss on Haskins, who still holds the flyweight belt.
Haskins started briskly, but was drawn into a toe-to-toe contest in round three and was caught with body shots.
Munyai cranked up the pressure and forced referee Mickey Vann to step in.
It was Munyai's second big victory on British soil.
The South African sprang a major surprise in June by stopping Martin Power to win the vacant Commowealth title.
Haskins - like Powers - was unable to deal with his size and was punished for his impatience when the fight rapidly turned into a close-contact war.