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Gould put together knocks of 57, 103, 77, 103, 100, 83, 103, 54 and 51 to dismantle the two-time semi-finalist in a virtuoso display. An out-of-sorts Maguire nearly conjured a maximum at 9-2 down but missed the 13th red in frame 12 and was out of the tournament just a frame later.
'I need to be patient' - McGill on defeat to Bingham at Crucible
The 38-year-old Gould, who has never been beyond the second round in Sheffield, will face Kyren Wilson in round two on Saturday.
Gould had considered retirement before the tournament but, after a resounding first-round performance, said he would only now consider retiring if he won the tournament outright.
"The only time it [the retirement speech] might pop out is if I am picking the trophy up at the end of the tournament – end on a high," said Gould.
Jamie Clarke stunned by 'absolutely crazy' World Championship win over Mark Allen
Mark Williams ended the first session of his World Snooker Championship clash against Stuart Bingham up 5-3.
Stuart Bingham misses frame-ball black to allow Mark Williams in
After Bingham won two of the first three frames against his fellow former champion, he was left kicking himself after missing a routine black, allowing the Welshman to draw level with him at 57-57 before potting a re-spotted black.
That started a run of four straight frames that went the way of Williams, featuring a high break of 97, when he was denied a century ironically by missing a routine black.
Bingham stemmed the tide by winning the final frame of the night's play, leaving the heavyweight tie finely poised ahead of its restart on Thursday.
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