Five-time champion Marshall was knocked out by fellow-Scot Stewart Anderson
Five-time champion Alex Marshall has been knocked out of the world indoor bowls, with fellow Scot Stewart Anderson winning a thrilling contest.
Qualifier Anderson progressed to the quarter-finals after a 4-10 9-4 2-1 win over the world number one, who was seeded second at Potters in Norfolk.
Marshall said: "It's really hard to take as I thought I played very well, but Stewart was absolutely relentless.
"If that guy plays like that, he is going to take some stopping."
Anderson, the world junior champion from Cumnock, sprung to prominence when reaching the semi-finals of last month's Scottish International Open as a qualifier.
I really can't believe it
He continued to impress in Norfolk when he knocked out 15th seed Mark McMahon in the second round but found it difficult to comprehend his achievement in beating Marshall, one of the greats of the game, who had won the mixed doubles title with Carol Ashby on Sunday.
"I really can't believe it," he told BBC Sport. "I knew that, if I played the way I have been playing, I can compete, but it's keeping it going that's the difficult bit."
Anderson joins fellow Scots and former world champions Paul Foster, the fourth seed, and David Gourlay, who is seeded sixth, in the quarter finals.
The defeat of Marshall was the latest in a series of surprises at Potters, which led to the second-round exit of reigning champion Billy Jackson, the top seed.
Jackson's conqueror, unseeded Canadian Hirendra Bhartu, was unable to reproduce his giant-killing form, however, losing to Jonathan Ross, the 16th seed from Ireland winning 9-5 8-3.
Jarrad Breen, the Welsh teenager, meets another non-seed, England's Nick Brett, in Wednesday's third-round ties.
Meanwhile, unseeded Australian Steve Glasson takes on English qualifier Robert Paxton on Thursday.
On Thursday, seventh seed Jason Greenslade faces unseeded fellow Welshman John Price.
Fifth seed Greg Harlow, of England, takes on Australian qualifier Ben Twist.