Tiresias was a brown horse standing 16 hands high[1] bred by his owner William Bentinck, 4th Duke of Portland a leading member of the Jockey Club who owned much of the land around Newmarket Racecourse.

[6] Tiresias was trained at Newmarket by the Duke's private trainer Richard Prince and ridden in most of his important races by the veteran jockey Bill Clift, whose strong but unsophisticated style was particularly effective on front-running horses.

On 12 April, the opening day of the Craven meeting, Tiresias started at odds of 1/3 for a 200 guinea Sweepstakes over one mile and defeated his only rival, the Duke of Grafton's Vanguard.

At the next meeting, Tiresias ran in the Newmarket Stakes on 30 April, in which his ten opponents included Antar, who had won the 2000 Guineas earlier in the week.

[11] The performances of Tiresias led to his being made favourite for the Derby, but doubts arose after he was decisively beaten in a "private" trial by his stable companion, Snake.

It was later pointed out that Tiresias, known to be an extremely difficult horse to ride, had been ridden in the trial by an inexperienced stable lad, who had been unable to control the colt effectively.

He was beaten in a one mile match race by Mr Vansittart's grey colt Financier, to whom he was attempting to concede three pounds.

[21] At the next Newmarket meeting two weeks later he claimed another 300 guinea prize, recording a "very easy" win over Pacha in a one mile match.

On 4 May at Newmarket, Tiresias won the Jockey Club Purse over the four mile Beacon Course, easily beating Aldford at level weights.