Darryl Fitton beat number two seed Alan Norris in a deciding set tie-break to reach the quarter-finals of the BDO World Championships.
The first six sets between Fitton and 2014 runner-up Norris went with the darts, the latter being pegged back on three occasions after edging ahead.
Norris missed three match darts, two of them in the last leg of the sixth set and another in the seventh.
Fitton missed four match darts before landing double eight for victory.
Needing to win the final set by two clear legs, the Stockport-born 52-year-old took it 4-2 to reach the quarter-finals for the sixth time in 13 appearances at Frimley Green.
He told BBC Sport: "Alan was awesome when he got to the final last year.
"But I know I've got the game in me and it means so much to me because I'm still in the tournament.
"I hit the doubles at the important times."
Swedish qualifier Peter Sajwani, who defeated top seed James Wilson in round one, was beaten 4-0 by a ruthless Robbie Green.
Sajwani hit a 139 checkout during the first set but it was only enough for one of just three legs that he won against the 16th seed from Wallasey.
Number four seed Scott Mitchell and three-time world champion Martin Adams are in second-round action on Wednesday evening.
Dutch third seed Aileen de Graaf's 2-0 win over England's Paula Jacklin concluded the first round of the women's draw.
All four women's quarter-final matches take place on Thursday.