Diamond Shoal was the second foal of his dam Crown Treasure, a daughter of Graustark who was sent to Europe in to be covered by Mill Reef and remained there for several years owing to import restrictions.

In October the colt was one of Britain's two representatives (alongside Awaasif) for the Washington, D.C. International Stakes at Laurel Park[6] where he finished fourth behind the French mare April Run.

[5] Diamond Shoal began his third season in the John Porter Stakes over one and a half miles at Newbury in April and recorded his first success in ten months as he won decisively by three lengths from Little Wolf.

Starting favourite he tracked the leaders before winning easily by one and a half lengths although he caused some alarm after passing the post when he swerved violently to the right.

He was then sent to Italy where he recorded a very easy four length victory over Easter Sun, in the Gran Premio di Milano, becoming the first British-trained to win the race since its inception in 1924.

[7] In early July, Diamond Shoal ran again in France when he contested the Group One Grand Prix de Saint-Cloud over 2500 metres.

He started at odds of 9.6/1 in a field which included Lancastrian (Prix Ganay), Electric, Zalataia (Oak Tree Invitational Stakes), Lemhi Gold and All Along.

Ridden by Steve Cauthen, Diamond Shoal raced in second behind Lemhi Gold before taking the lead 300m from the finish and winning comfortably by three-quarters of a length from Lancastrian with Zalataia in third place.

[8] On 23 July Diamond Shoal was one of nine horses to contest the thirty-third running of Britain's most prestigious all-aged race, the King George VI and Queen Elizabeth Stakes over one and a half miles at Ascot.

He held off challenges from Awaasif and Sun Princess and looked the likely winner before being overtaken inside the final furlong and was beaten three-quarters of a length by Time Charter.

[9] On 4 September Diamond Shoal ran in Germany again in the Grosser Preis von Baden in which he was matched against the leading German three-year-old Abary.

[7] At the end of his racing career, Diamond Shoal was syndicated and retired to become a breeding stallion at the Walmac-Warnerton farm in Kentucky at an initial fee of $25,000.