Doncaster's dam Marigold had a fairly good career on the track, and was sired by The Derby winner Teddington.

[2] Doncaster, a chestnut with a white blaze originally named "All Heart and No Peel", was raised at the Sledmere Stud before he was sent to the Tattersalls auction.

James Merry bought the colt for 950 guineas, changed his name to Doncaster (after the racecourse), and sent him to trainer Robert Peck.

The Duke had been searching for a stallion prospect, with a good pedigree and racing record, to stand at his Eaton Stud in Cheshire.

Doncaster was bred to the mare Lily Agnes (by Macaroni), who produced the filly Farewell, a 1,000 Guineas winner.