In 2007, Chagaev pulled out of a unification bout against then-WBO champion Sultan Ibragimov.

BBC: Chagaev pulled from Valuev fight

Briggs won the WBO title with a 12th-round knockout of Sergei Liakhovich in November 2006 but lost the title in his first defence against Sultan Ibragimov eight months later.

BBC: Vitali Klitschko (left) and Shannon Briggs

In February 2008, Wladimir beat Russia's Sultan Ibragimov to take the WBO crown - and his last fight was a seventh-round stoppage of former world champion Hasim Rahman in December.

BBC: Haye 'an embarrassment to boxing'

Between the two of them, the list of the people they successfully fought includes Lennox Lewis, Danny Williams, Corrie Sanders, Chris Areola, Sultan Ibragimov, Calvin Brock, Lamon Brewster, and Samuel Peter.

FORBES: Is Politics the New Boxing?