"It feels great," Clayton said. "Some people probably didn't think I'd make it this far, but I showed them as long as we do the work and want it, we can succeed in whatever we want to do."
Clayton, a 24-year-old welterweight from Dartmouth, N.S., earned Canada's first Olympic boxing victory in eight years in his first bout with a 12-8 decision over Mexico's Oscar Molina.
The Dartmouth native has trained under his great-uncle, Gary Johnson, and Kirk Johnson, the 1992 Canadian Olympian.
"Coming up through the last round the coach asked me 'How much do you want it? Show everybody how much you want it.' I knew I trained hard and knew how much I had left and gave it everything I had."
Clayton will take on Britain's Freddie Evans in the quarters on Aug. 7.
Evans beat fourth-seeded Egidijus Kavaliauskas of Lithuania 11-7 in the afternoon session. The home crowd cheered wildly for every big punch by the British team, which is riding a wave of hometown that seems awfully similar to the momentum that carried China to four medals in Beijing.
"I've never experienced anything like it before," the 21-year-old Welshman Evans said of the London crowd's support. "It really gives you a bit of a boost. … They're all top lads here, but I'm confident that I can come back again and keep doing it."
Canada's other men's boxing competitor, Simon Kean of Trois-Rivieres, Que. had already advanced to the quarter-finals. He will meet Ivan Dychko of Kazakhstan on Monday in a 91-kilogram super heavyweight bout.
The Canadian to win silver in the Olympic boxing ring was Nova Scotian David Defiagbon. The last fighter born in Canada to take home a medal was the late Mark Leduc, who won silver at the 1992 Barcelona Games.
Spence lone hope for U.S.
A few hours after the U.S. men's boxing team thought it was done at the Olympics, amateur boxing's governing body decided Errol Spence deserved to fight on.
AIBA overturned Spence's loss to Indian welterweight Krishan Vikas late Friday night, five hours after the defence-minded Vikas had apparently clutched and grabbed his way to a 13-11 victory.
After the American team protested the result, AIBA's competition jury reviewed the bout and ruled Vikas had committed nine holding fouls in the third round alone. He also intentionally spit out his mouthpiece in the second round, which should have resulted in at least four points of deductions.
Spence advanced into the quartes to face Russia's Andrey Zamkovoy on Tuesday.
American flyweight Rau'shee Warren lost his opening bout in his record third Olympics, falling to France's Nordine Oubaali 19-18.
For Warren, it is a third consecutive Games experience in which he lost his opening bout.
The U.S. team won just one bronze medal in Beijing, its worst showing.