His major breakthrough was beating John Lowe in the semi-finals of the 1983 British Open in which he finished runner-up to Eric Bristow.
He made his World Championship debut in 1984 and reached the quarter-final, losing heavily 0–5 to Jocky Wilson.
He made his first semi-final in 1990, losing to Eric Bristow and his only final appearance came in 1992 – when he lost an epic match 5–6 in sets to Taylor.
[2] Gregory won the bull-off to throw first in the decider, but had a bounce-out on his first turn and Taylor comfortably sealed the win.
Gregory would become the only man to have lost a World Championship final having had darts at double to win, and remained so until Mark McGeeney did so in 2018.
[7] Gregory won the second WDC Lada UK Masters in November 1993, defeating Bob Anderson in the final.
[10] John Lowe felt that Gregory had succumbed to pressure from Olly Croft, who warned that he would lose his house if the WDC lost its case.
Gregory's return to the BDO was in time for the 1994 British Open, which was staged on New Year's Day, and he reached the semi-finals.
He was not able to compete at the Embassy World Darts Championship in 1994, as the tournament draw had been made before he decided to return to the BDO.
In the semi-final, Gregory defeated the reigning BDO World Champion, Richie Burnett, and beat Peter Manley in the final.
He suffered first round defeats in each of his next three appearances in the BDO World Championship at Lakeside – in 1996, 1997 and 1999, and did not qualify for the competition again.