Amir Khan made sure of at least a bronze medal in the lightweight boxing division with a stunning victory over South Korea's Baik Jong-sub.
Baik tried to rush the 17-year-old Briton from the bell but was dropped by a sweet right hand after 60 seconds.
The referee stopped the fight with 23 seconds remaining in the first round following another right-hand peach.
"I've matched my ambitions by getting a medal - so now let's go for a silver or better," said an elated Khan.
Khan's semi-final opponent on Friday will be Kazakhstan's Serik Yeleuov, who beat Domenico Valentino of Italy 29-23 in the previous bout.
"We just got the tactics right, to get in and get out because he's a strong lad," said Khan.
"And I finished him in the first round! It was a very good punch that hurt him - a plum right hand.
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I am now sure that he can go all the way
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GB coach Terry Edwards
"It's a dream come true. Everyone wanted to see me on the podium and I want to show everyone that I'm the best in the world.
"The pressure is off me now."
British coach Terry Edwards said: "We expected the fight to go that way in the third round. That it did in the first was a bonus.
"Amir came for the experience and he has proved himself. I am now sure that he can go all the way."
Meanwhile, lightweight favourite and two-time Olympic champion Mario Kindelan disposed of Rovshan Huseynov of Azerbaijan 23-11 in his quarter-final clash.
The 33-year-old Kindelan now faces Russia's Murat Khrachev who outpointed Sam Rukundo of Uganda 31-18.