After teaching 'A' Level students for five years in Dorset, England, his private commissions increased sufficiently to enable him to devote all his time to painting, and for two years he specialised in figure studies. After a series of jobs in the late sixties and early seventies, he turned freelance in 1973. In 1988, he moved to Somerset and started to produce some of his most successful work. Every year from 1990 to 1993 he was decorated by the 'American Academy of Equine Artists' - in 1993 he received a trio of awards: 'Best Racing Picture', 'Best Sporting Picture' and 'Most Popular Picture'.
Regular exhibitions throughout the U.K and U.S.A, together with his acceptance into both the 'American Academy of Equine Art' and the 'Society of Equine Artists', have resulted in his work being highly sought after both at home and abroad. In 1990 his painting, 'The Prince of Wales Cup', featuring Prince Charles playing polo, was auctioned in aid of the Friends of Conservation charity for $29,000 in Florida.
Charles Lane, Horse & Hound, said: "Graham Isom's style is always changing, if almost imperceptibly, and a recent less-rigid delineation and softer use of colour now gives his paintings much more warmth than in the past, without detracting from a tremendous ability to paint horses in action."