Battle Of Marengo was left generally unchanged by bookmakers for Classic glory after a workmanlike success in the Derrinstown Stud Derby Trial at Leopardstown.
Giving Aidan O'Brien his fourth Derby trial winner of the week, the Galileo colt - sent off at prohibitive odds of 2-13 - took over from Dont Bother Me around five furlongs out and it looked like he would win with real ease when going clear with quarter of a mile to run.
He had to get a reminder from Joseph O'Brien, however, and in the end was pushed out to beat Loch Garman, with Little White Cloud running an eyecatching race in third.
A length and three-quarters was the winning margin and O'Brien senior said: "That all went to plan. We had to go on with him or it would have been a very steady pace.
"He has just ticked over since the last day. You would have to be happy with him. He is lazy in front but he gave a good blow afterwards. He loves fast ground as he is a great mover.
"The three owners will decide where he goes next. It's going to be an interesting Dante now (at York on Thursday)."
O'Brien is expected to run Leopardstown maiden winner Indian Chief in the Knavesmire feature.
Coral and William Hill kept Battle Of Marengo at his respective pre-trial price for the Investec Derby on June 1.
David Stevens for Coral said: "His backers would surely have hoped for a more impressive performance, although the betting suggests he remains the leading Ballydoyle contender following a week in which the team have won all four colts' trials."
But Stan James were more impressed, cutting Battle Of Marengo to 4-1 second-favourite from 5-1. Spokesman Joseph Burke said: "There are no stamina doubts regarding Battle of Marengo whatsoever and he appears to possess just the right combination of speed and staying power to win a Derby."