The great and good of the boxing world turned out to watch the momentous occasion, with Roy Jones Jr and Frank Bruno among those at ringside.
WBO interim heavyweight champion Joseph Parker was also keeping a close eye on proceedings as he seeks a date with Usyk next.
Usyk, who has called the UK his second home, was welcomed warmly after Dubois had also been cheered to the ring.
It took no time for the fight to spark into life as Dubois doubled up on his jab but it was clear that Usyk wasn’t going to be a sitting target. The former undisputed cruiserweight champion was far too slick, ducking under the jab and punishing Dubois regularly.
Southpaw Usyk punctuated each of the opening two rounds with a counter left and had Dubois looking a little unsteady in the second.
Dubois looked out of the ring to his father Stan between rounds for some advice but he still found it difficult to pin down the 2012 Olympic gold medallist.
Usyk unloaded in the fifth and sent Dubois tumbling to the canvas with a crisp left.
Dubois showed incredible spirit to beat the count but the writing was already on the wall.
Another trusty left hook landed clean on Dubois’ chin and his corner threw in the towel as the referee reached the count of nine.
