Spencer started his snooker career at the age of 15. Snooker was in decline during his youth, and he did not turn professional until his early 30s, when interest in the game started to revive. He first won the World Championship in 1969 after being loaned £100 by his bank to raise the entry fee. He battled for supremacy throughout the 1970s with Ray Reardon and Alex Higgins as snooker emerged from a phase of obscurity to become one of Britain’s most popular sports. Spencer went on to win two further world titles, the last of which was the historic inaugural event at the Crucible Theatre in Sheffield in 1977. He won many other titles including Pot Black three times and the Masters once. He never reached the top of the world rankings, however, always being eclipsed by his friend and rival, Reardon.

In January 1982, Spencer was Steve Davis's opponent when Davis made the first televised 147 at the Lada Classic tournament at the Queen Elizabeth Hall, Oldham. Ironically, Spencer had himself made a 147 at a televised event three years earlier, but the cameramen were on their tea break at the time and the table and ball set were not at the correct standard.

Spencer was the first professional snooker player to use a two-piece cue, which he used to win the 1977 title.His cue action included an unusually long backswing which gave him immense cue power, and allowed him to develop new shots using screw and side spin which aided the progression to modern break-building.

He was the owner of Spencer's Snooker Club in Bolton in the 1980s, when snooker was at its peak popularity. Spencer was also a commentator on snooker for BBC television for many years, and was chairman of the WPBSA for six years from 1990.

Spencer retired from snooker suffering from myasthenia gravis (with symptoms including double vision) in 1991. In 2003 he was diagnosed with stomach cancer but he later refused treatment for it in order to enjoy the rest of his life free from the effects of chemotherapy. He had for many years been a dedicated charity fundraiser and, despite his illness, he took part in a sponsored parachute jump in 2005. His biography was published that same year, entitled Out Of The Blue And Into The Black.

Spencer's battle with cancer ended on 11 July 2006 when he died in a hospice in Radcliffe at the age of 70.

Ranking wins

• World Championship — 1977

Non-ranking wins

• World Championship — 1969, 1971 (World Snooker Championship did not become a ranking tournament until 1974)
• Benson & Hedges Masters — 1975
• Canadian Open — 1976
• Irish Masters — 1978
• Norwich Union Open — 1973, 1974
• Holsten Lager International — 1979
• Pontin's Professional — 1977
• Pot Black — 1970, 1971, 1976
• Classic — 1980
• Australian Masters — 1980

Team wins

• World Cup with England team — 1981

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