Ukraine's Oleksandr Usyk celebrates winning the undisputed world heavyweight boxing title fight against Britain's Daniel Dubois, in London.

Ukraine's Oleksandr Usyk celebrates winning the undisputed world heavyweight boxing title fight against Britain's Daniel Dubois in London.

Ukraine's Oleksandr Usyk celebrates winning the undisputed world heavyweight boxing title fight against Britain's Daniel Dubois in London.

Daniel Dubois lies on the ring after a knockout by Ukraine's Oleksandr Usyk during their world heavyweight boxing title fight, in London.

Ukraine's Oleksandr Usyk takes a swig of water after winning the undisputed world heavyweight boxing title fight against Britain's Daniel Dubois, in London.

Ukraine's Oleksandr Usyk, right, lands a left on Britain's Daniel Dubois their world heavyweight boxing title fight, in London.

Ukraine's Oleksandr Usyk, right, and Britain's Daniel Dubois in action during the undisputed world heavyweight boxing title fight in London.

Britain's Daniel Dubois is in on the floor after a knockout by Ukraine's Oleksandr Usyk during the undisputed world heavyweight boxing title fight In London.

Ukraine's Oleksandr Usyk, left, and Britain's Daniel Dubois in action during the undisputed world heavyweight boxing title fight in London.

Ukraine's Oleksandr Usyk, right, and Britain's Daniel Dubois in action during the undisputed world heavyweight boxing title fight in London.