After a promising start to his career as an amateur and assistant professional, he had one exceptional year, 1967, when he won the Harry Vardon Trophy and played in the Ryder Cup, but had only limited success afterwards.

[6] In 1963 he reached quarter-finals of the News of the World Match Play and was runner-up, with Tony Jacklin, in the Coombe Hill Assistants' Tournament.

[9] The event was reduced to 54 holes after the second round was abandoned because of bad weather, Gregson winning by three strokes from Richard Davies and Hedley Muscroft.

[12][13] Returning to England he won the Schweppes PGA Championship at the end of the month, with rounds of 67 and 65 on the final day to beat Hugh Boyle by three strokes.

[14] In June he won the Daks Tournament at Wentworth, beating Neil Coles by two strokes, after final day rounds of 67 and 66, and was a joint winner of the Martini International with Brian Huggett.

[15][16] Qualification for the British team for the 1967 Ryder Cup was based on a points system using performances in 1966 and 1967, finishing after the 1967 Open Championship.

[24] Gregson made the top one hundred on the Order of Merit in each of the European Tour's first nine official seasons from 1972 to 1980.

[29] Gregson was a regular competitor on the Safari Circuit, winning the 1974 Cock o' the North in Zambia, beating Jack Newton in a playoff.