Defending champion Greg Harlow reached the International Open quarter-finals with an 8-5 8-5 win over Billy Jackson.
Harlow is the current world number one
The 38-year-old from Ely is chasing a record third title at Sheffield's Ponds Forge International Sports Centre.
Harlow raced to a 7-0 first-set lead before Lincoln's Jackson got going. The second was a closer affair but the world number one pulled through.
He now takes on Welsh qualifier Richard Morgan who ousted seventh seed Ian Bond from Devon 8-5 9-5.
Scottish sixth seed Alex Marshall fell to a 9-3 8-7 defeat at the hands of sixth-seeded Irishman Jonathan Ross.
Marshall's compatriot, fifth seed Paul Foster, dropped a set before reaching the last eight with a 10-1 3-8 2-1 triumph over Kiwi qualifier Jamie Hill.
Friday's quarter-final line-up:
 Mervyn King (Eng) v  Mark McMahon (Eng)
 David Gourlay (Aus) v  Jonathan Ross (Ire)
 Greg Harlow (Eng v [Q] Richard Morgan (Wal)
 Paul Foster (Sco) v  Mark Royal (Eng)