Billy Joe Saunders produced the best performance of his career to comprehensively outpoint Turkey's Adem Kilicci 14-3, in the 69kg round of 32.
Turk Kilicci, who won a bronze medal at the World Championships in Chicago last year, never got to grips with the southpaw style of the youngest member of the British boxing team and Saunders picked him off on the counter time and time again.
Saunders took the first round 2-0 and simply grew in confidence as the contest progressed. A hard straight left counter rocked the Turk in the second and by the end of the round he was 6-1 in front.
Kilicci was understandably anxious at the start of the third session but Saunders was more than comfortable off the back foot, reverting to offense when he saw the opportunities. He simply exuded class and confidence as the third session closed with him 11-2 ahead.
Disheartened and confused, Kilicci tried to step it up but Saunders footwork and defensive body movement was exemplary - 14-3 was a fair reflection of the Briton's dominance though it must be said the scoring is somewhat erratic.
The youngster from Hertford, still only 18, was not expected to progress but showed maturity well beyond his years to set up a contest with Cuban Carlos Banteur, who he beat on a countback in the Strandja Memorial tournament in January.
Saunders surprised everyone by winning every round to take the contst 14-3
Elsewhere Ireland's Johhny Joyce also caused an upset by outpointing Hungarian Gyula Kate 9-5. Kate had beaten Joyce on their three previous meetings.