Sulllivan vs Corbett was not the first Gloved match for the world's heavyweight champ

The key events are as follows:

Jem Mace efectivley created the world title when he defeated Tom Allen in America, to unify the British and American titles. After this, two things happened.

1. There was a major crackdown on prizefightiung in Britain, which forced most of the best British prizefighters to settle in America.
2. Mace conducted his defences of both titles in the United States.

This caused many people to view the American title as now effectivley being the world title. When Mace retired, there was no way that a fight for the vacant title was going to happen anywhere but America. Tom Allen and Joe Goss were matched to fight for the vacant American/world title (note that both were born in Britain). Tom Allen had been the previous American title holder, and Joe Goss was the man that Mace had beaten to win the vacant British title, after Tom King retired. With Mace out of the way, it was credible that a fight between them in the only possible venue could be seen as being for the world title.

After the effective disolution of the British title and its incorporation into the American title, another British title claim emerged with Charlie Mitchell. It did not however trace its line back to the previous title claim held by Mace. Sullivan did beat two Britiush Champions of this lineage in Mitchell and Greenfield in gloved bouts.