Thorburn had defeated Virgo 6–1 in the round robin phase of the 1980 Bombay International, but lost 7–13 to him in the final. He won 5–3 against Virgo in the first round of the 1980 Masters, then lost 3–5 to Griffiths in the quarter-final. In advance of the 1980 World Championship, he practiced at a club near the Crucible that was owned by a friend, and gave up smoking and drinking alcohol for a week before the tournament. His first match was against Mountjoy, with Thorburn finishing their first session 3–5 behind. In the evening, he played cards and drank alcohol with friends until 5:00 am, resuming the match the next day by winning the first five frames in succession. Thorburn won the match 13–10. In the quarter-final, he beat Jim Wych 13–6, having led 5–3, 9–3 and 10–6. He led David Taylor 5–3 after their first semi-final session, and 11–4 at the end of the second. In the last session of the match, Thorburn extended his lead to 15–7 by the mid-session interval, then won 16–7 with a break of 114 in the 23rd frame.