Universally Recognised Heavy-Weight Boxing Champions

This may be contentious however I have tried to create a list of those Heavy-Weight Boxers who were universally acknowledged as the reigning world champion at the time they held the title. The introduction of different Boxing organisations, all of which claimed to be the "one true world boxing body" led to the ridiculous situation of up to 4 boxers at any one time claiming to be the "World Champion". This explains gaps in the times between some title holders. Note - even though he won his first title as Cassius Clay, I have included his later name of Muhammad Ali. In the case of title holders who lost and then regained their titles, I have only included the one (first) entry. Enjoy!