Empire Maker, who is owned by Juddmonte Farms, had to work hard for his victory down the finishing straight to peg back Funny Cide.

Jockey Jerry Bailey did as little urging as possible and Empire Maker stretched out to take the 750,000 race by half a length.

The three-year-old son of Unbridled was following up a decisive nine-and-three-quarter-length win in the Florida Derby last month and Frankel was pleased to see his charge handle a rain-soaked surface for the first time.

He told the Thoroughbred Times: “Jerry gave me a few anxious moments but you could see what he wanted to do.

“He didn’t want to bottom him out for this race. He tried to make him win as easy as possible without taking too much out of him.

“He answered a lot of questions today.”

Frankel made it a double at Keeneland as the front-running Peace Rules landed his 750,000 Derby trial.

Peace Rules has won both his starts this term, including the Grade Two Louisiana Derby last time.

The son of Jules moved clear of Brancusi to win by three and a half lengths under Edgar Prado and Frankel admitted he is in an admirable position for the Derby, which is due to be run on May 3 at Churchill Downs.

“I’m in a good spot. It looks easy when you write about it and everything. We still have to get there and run around the racetrack.

“Peace Rules ran really well – the only question about him is the distance. But he looked fairly strong coming out of this race. The inside post sure helped him,” Frankel added.