Champion trainer Aidan O'Brien has completed another Guineas double with Hermosa dominating the 1000 Guineas at Newmarket.

It is the fourth time the Irishman has won both opening Classics of the season with Magna Grecia taking the colts division a day earlier, the 2000 Guineas, on Saturday (Sunday AEST).

A 14-1 chance, Hermosa looked sure to be swamped as other runners moved up but she found under pressure and began to pull away up the rise under Wayne Lordan to beat Lady Kaya by a length.

"We are delighted. She did very well over the winter, and she ran an unbelievable race last year in the Fillies' Mile," O'Brien said.

"She is very uncomplicated. She is tough and, like her sister (Hydrangea), stays well. Wayne gave her a great ride, and it is credit to everyone at home.

"Physically she has changed a lot over the winter and really grew into a three- year-old. She is a tough filly. The plan was to go along (in front) with her, and she was happy to go, because we knew she would get the trip well."

Hermosa is now as short as 5-1 to win the Oaks at Epsom.