Dennis was born in Coalisland, Co. Tyrone in Northern Ireland and started playing snooker when he was nine and was the local senior champion at 14. He moved to England in 1966 and lived near Blackburn in Lancashire. In 1968 he won the national under-19 billiards championship. He played in one amateur international for England before turning professional in November 1972. His first professional event was the 1973 world championship when he lost in the first round 8-9 to Cliff Thorburn. He failed to qualify in 1974 but the following year reached the semi-finals where Eddie Charlton beat him 19-12. 1977 saw him in another semi-final but in 1978 he went out in the first round of both the world and UK championships. It was in 1979 that he made it to his first final, at the Crucible, against Terry Griffiths, in the world championship. He lost 24-16.

His career continued in much the same vein for the next few years: a few semi-finals, the odd final, but never actually winning anything. In one of those finals, the 1981 Jameson International, he was embarrassed to be whitewashed 9-0 by Steve Davis. Nevertheless he was becoming one of the most consistent players on the circuit and was ranked at number two in 1979/80. In 1980 came some modest success when he successfully challenged Alex Higgins for the Irish Professional title and successfully defended it the following year before winning the first of the new knock-out style championships in 1982. He went to win that title three more times in 1985, 86 and 87. Still a major victory eluded him.

Success was to come in his 13th season as a professional, 1984/5 and strangely, it was the sudden death of his mother which was to be his inspiration. Because of this he pulled out of the first ranking event that season, the Jameson International, after reaching the quarter-finals. Also he had since the spring of 1983, been using those famous ‘upside down’ glasses which have since become his trade mark. The next tournament was the Rothmans Grand Prix at the Hexagon in Reading. Dennis did not want to play but his family persuaded him. The whole nation shared his tears of joy as he beat Cliff Thorburn for his first major title. Still better was to come, of course, and the season ended with that famous win over Steve Davis to make him champion of the world.

Although he lost in the opening round at the Crucible the following year, and did not win another ranking event, he did win the Masters at Wembley in 1987 and the Canadian Masters twice. Even without ranking victories, he managed to keep his place in the top 16 until the end of the 1993/4 season, having been ever present in that elite group since rankings were introduced in 1976. He was becoming more and more involved as a commentator and early exits from most tournaments facilitated this. At the 1999 world championships he announced his retirement but in the event decided to have just one more season. No success came his way and a year later he definitely put away his cue.

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