Both fighters remained calm throughout the news conference, which began 48 minutes later than scheduled, leaving their respective teams to throw out jibes.
Usyk is yet to taste defeat in 23 fights as a professional and has won his three previous bouts in London, although none of them have taken place at Wembley Stadium.
He has fond memories of London as an amateur too, having won heavyweight gold at the 2012 Olympics.
Dubois has won three fights in a row since losing to Usyk with his most recent coming at the national stadium when he stunned Anthony Joshua in September.
“Right now I just want to get it on,” Dubois said.
“I’m going to write my own script. They’ve got their script and I’ll write my own. I’m going to win these belts and I’m going to be the man.”
Dubois has picked up 21 knockouts in 22 victories with just two defeats on his record.
Lennox Lewis was the last Briton to hold undisputed status at heavyweight in 1999 but Dubois, if successful, will become the first to achieve that feat in the four-belt era.
